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 $68.44   9.520%   $74.9555   $74.96   $74.95   $75.00  
  Purchase #2 $188.81   8.234%   $204.3566   $204.36   $204.35   $204.40  
  Purchase #3 $123.70   7.645%   $133.1569   $133.16   $133.15   $133.20  
  Purchase #4 $245.71   8.841%   $267.4332   $267.43   $267.45   $267.40  
  Purchase #5 $223.91   3.862%   $232.5574   $232.56   $232.55   $232.60  
  Purchase #6 $57.71   4.278%   $60.1788   $60.18   $60.20   $60.20  
  Purchase #7 $134.93   4.660%   $141.2177   $141.22   $141.20   $141.20  
  7 purchase totals = $1,043.21       $1,113.8561   $1,113.87   $1,113.85   $1,114.00