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 $87.62   8.428%   $95.0046   $95.00   $95.00   $95.00  
  Purchase #2 $71.85   10.129%   $79.1277   $79.13   $79.15   $79.10  
  Purchase #3 $30.83   11.534%   $34.3859   $34.39   $34.40   $34.40  
  Purchase #4 $11.97   9.734%   $13.1352   $13.14   $13.15   $13.10  
  Purchase #5 $22.67   10.469%   $25.0433   $25.04   $25.05   $25.00  
  Purchase #6 $246.94   11.863%   $276.2345   $276.23   $276.25   $276.20  
  Purchase #7 $212.96   3.786%   $221.0227   $221.02   $221.00   $221.00  
  7 purchase totals = $684.84       $743.9539   $743.95   $744.00   $743.80