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 $95.63   3.132%   $98.6251   $98.63   $98.65   $98.60  
  Purchase #2 $33.80   4.862%   $35.4434   $35.44   $35.45   $35.40  
  Purchase #3 $87.96   9.182%   $96.0365   $96.04   $96.05   $96.00  
  Purchase #4 $110.85   5.275%   $116.6973   $116.70   $116.70   $116.70  
  Purchase #5 $90.76   13.343%   $102.8701   $102.87   $102.85   $102.90  
  Purchase #6 $161.44   13.258%   $182.8437   $182.84   $182.85   $182.80  
  Purchase #7 $237.56   7.472%   $255.3105   $255.31   $255.30   $255.30  
  7 purchase totals = $818.00       $887.8266   $887.83   $887.85   $887.70