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 $191.46   5.487%   $201.9654   $201.97   $201.95   $202.00  
  Purchase #2 $6.75   7.643%   $7.2659   $7.27   $7.25   $7.30  
  Purchase #3 $116.64   13.539%   $132.4319   $132.43   $132.45   $132.40  
  Purchase #4 $22.72   13.160%   $25.71   $25.71   $25.70   $25.70  
  Purchase #5 $89.55   3.344%   $92.5446   $92.54   $92.55   $92.50  
  Purchase #6 $114.62   4.548%   $119.8329   $119.83   $119.85   $119.80  
  Purchase #7 $220.90   5.132%   $232.2366   $232.24   $232.25   $232.20  
  7 purchase totals = $762.64       $811.9873   $811.99   $812.00   $811.90