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 $206.71   13.828%   $235.2939   $235.29   $235.30   $235.30  
  Purchase #2 $99.54   11.134%   $110.6228   $110.62   $110.60   $110.60  
  Purchase #3 $247.65   11.610%   $276.4022   $276.40   $276.40   $276.40  
  Purchase #4 $217.26   5.115%   $228.3728   $228.37   $228.35   $228.40  
  Purchase #5 $62.65   6.486%   $66.7135   $66.71   $66.70   $66.70  
  Purchase #6 $182.69   5.853%   $193.3828   $193.38   $193.40   $193.40  
  Purchase #7 $62.41   4.667%   $65.3227   $65.32   $65.30   $65.30  
  7 purchase totals = $1,078.91       $1,176.1107   $1,176.09   $1,176.05   $1,176.10