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 $69.34   10.655%   $76.7282   $76.73   $76.75   $76.70  
  Purchase #2 $94.77   7.579%   $101.9526   $101.95   $101.95   $102.00  
  Purchase #3 $232.26   5.138%   $244.1935   $244.19   $244.20   $244.20  
  Purchase #4 $36.96   12.175%   $41.4599   $41.46   $41.45   $41.50  
  Purchase #5 $229.94   13.667%   $261.3659   $261.37   $261.35   $261.40  
  Purchase #6 $202.79   8.339%   $219.7007   $219.70   $219.70   $219.70  
  Purchase #7 $197.53   9.534%   $216.3625   $216.36   $216.35   $216.40  
  7 purchase totals = $1,063.59       $1,161.7633   $1,161.76   $1,161.75   $1,161.90