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 $186.29   4.821%   $195.271   $195.27   $195.25   $195.30  
  Purchase #2 $65.99   3.690%   $68.425   $68.43   $68.45   $68.40  
  Purchase #3 $217.82   10.417%   $240.5103   $240.51   $240.50   $240.50  
  Purchase #4 $129.74   8.549%   $140.8315   $140.83   $140.85   $140.80  
  Purchase #5 $69.42   11.579%   $77.4581   $77.46   $77.45   $77.50  
  Purchase #6 $183.28   5.817%   $193.9414   $193.94   $193.95   $193.90  
  Purchase #7 $232.73   11.233%   $258.8726   $258.87   $258.85   $258.90  
  7 purchase totals = $1,085.27       $1,175.3099   $1,175.31   $1,175.30   $1,175.30