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 $84.87   12.287%   $95.298   $95.30   $95.30   $95.30  
  Purchase #2 $141.37   9.811%   $155.2398   $155.24   $155.25   $155.20  
  Purchase #3 $111.73   6.344%   $118.8182   $118.82   $118.80   $118.80  
  Purchase #4 $57.65   4.332%   $60.1474   $60.15   $60.15   $60.10  
  Purchase #5 $124.78   10.365%   $137.7134   $137.71   $137.70   $137.70  
  Purchase #6 $14.51   7.355%   $15.5772   $15.58   $15.60   $15.60  
  Purchase #7 $223.93   5.721%   $236.741   $236.74   $236.75   $236.70  
  7 purchase totals = $758.84       $819.5350   $819.54   $819.55   $819.40