Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $174.25   12.836%   $196.6167   $196.62   $196.60   $196.60  
  Purchase #2 $232.98   10.716%   $257.9461   $257.95   $257.95   $257.90  
  Purchase #3 $181.59   12.426%   $204.1544   $204.15   $204.15   $204.20  
  Purchase #4 $177.56   10.512%   $196.2251   $196.23   $196.25   $196.20  
  Purchase #5 $240.87   10.804%   $266.8936   $266.89   $266.90   $266.90  
  Purchase #6 $116.69   5.660%   $123.2947   $123.29   $123.30   $123.30  
  Purchase #7 $228.32   10.371%   $251.9991   $252.00   $252.00   $252.00  
  7 purchase totals = $1,352.26       $1,497.1297   $1,497.13   $1,497.15   $1,497.10