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 $87.43   9.735%   $95.9413   $95.94   $95.95   $95.90  
  Purchase #2 $212.81   10.615%   $235.3998   $235.40   $235.40   $235.40  
  Purchase #3 $154.84   3.155%   $159.7252   $159.73   $159.75   $159.70  
  Purchase #4 $80.73   4.323%   $84.22   $84.22   $84.20   $84.20  
  Purchase #5 $140.28   6.465%   $149.3491   $149.35   $149.35   $149.30  
  Purchase #6 $161.92   13.469%   $183.729   $183.73   $183.75   $183.70  
  Purchase #7 $84.34   4.369%   $88.0248   $88.02   $88.00   $88.00  
  7 purchase totals = $922.35       $996.3892   $996.39   $996.40   $996.20