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 $178.45   13.211%   $202.025   $202.03   $202.05   $202.00  
  Purchase #2 $217.98   5.490%   $229.9471   $229.95   $229.95   $229.90  
  Purchase #3 $213.71   5.513%   $225.4918   $225.49   $225.50   $225.50  
  Purchase #4 $140.32   8.466%   $152.1995   $152.20   $152.20   $152.20  
  Purchase #5 $186.70   9.780%   $204.9593   $204.96   $204.95   $205.00  
  Purchase #6 $246.74   7.112%   $264.2881   $264.29   $264.30   $264.30  
  Purchase #7 $179.59   9.791%   $197.1737   $197.17   $197.15   $197.20  
  7 purchase totals = $1,363.49       $1,476.0845   $1,476.09   $1,476.10   $1,476.10