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 $184.33   5.781%   $194.9861   $194.99   $195.00   $195.00  
  Purchase #2 $63.31   3.801%   $65.7164   $65.72   $65.70   $65.70  
  Purchase #3 $97.92   6.828%   $104.606   $104.61   $104.60   $104.60  
  Purchase #4 $240.38   13.853%   $273.6798   $273.68   $273.70   $273.70  
  Purchase #5 $201.26   11.477%   $224.3586   $224.36   $224.35   $224.40  
  Purchase #6 $60.46   9.667%   $66.3047   $66.30   $66.30   $66.30  
  Purchase #7 $17.70   6.103%   $18.7802   $18.78   $18.80   $18.80  
  7 purchase totals = $865.36       $948.4318   $948.44   $948.45   $948.50