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 $84.44   12.833%   $95.2762   $95.28   $95.30   $95.30  
  Purchase #2 $159.63   5.241%   $167.9962   $168.00   $168.00   $168.00  
  Purchase #3 $127.90   11.200%   $142.2248   $142.22   $142.20   $142.20  
  Purchase #4 $128.63   7.344%   $138.0766   $138.08   $138.10   $138.10  
  Purchase #5 $81.49   7.273%   $87.4168   $87.42   $87.40   $87.40  
  Purchase #6 $119.35   5.500%   $125.9143   $125.91   $125.90   $125.90  
  Purchase #7 $161.42   10.788%   $178.834   $178.83   $178.85   $178.80  
  7 purchase totals = $862.86       $935.7389   $935.74   $935.75   $935.70