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 $85.93   13.198%   $97.271   $97.27   $97.25   $97.30  
  Purchase #2 $218.67   8.293%   $236.8043   $236.80   $236.80   $236.80  
  Purchase #3 $218.84   9.202%   $238.9777   $238.98   $239.00   $239.00  
  Purchase #4 $127.46   7.468%   $136.9787   $136.98   $137.00   $137.00  
  Purchase #5 $133.80   3.598%   $138.6141   $138.61   $138.60   $138.60  
  Purchase #6 $89.33   7.412%   $95.9511   $95.95   $95.95   $96.00  
  Purchase #7 $210.91   5.142%   $221.755   $221.76   $221.75   $221.80  
  7 purchase totals = $1,084.94       $1,166.3519   $1,166.35   $1,166.35   $1,166.50