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 $87.39   7.497%   $93.9416   $93.94   $93.95   $93.90  
  Purchase #2 $212.42   5.612%   $224.341   $224.34   $224.35   $224.30  
  Purchase #3 $47.78   12.733%   $53.8638   $53.86   $53.85   $53.90  
  Purchase #4 $159.92   9.221%   $174.6662   $174.67   $174.65   $174.70  
  Purchase #5 $98.61   7.356%   $105.8638   $105.86   $105.85   $105.90  
  Purchase #6 $175.64   12.166%   $197.0084   $197.01   $197.00   $197.00  
  Purchase #7 $9.63   9.137%   $10.5099   $10.51   $10.50   $10.50  
  7 purchase totals = $791.39       $860.1947   $860.19   $860.15   $860.20