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 $234.44   5.212%   $246.659   $246.66   $246.65   $246.70  
  Purchase #2 $155.89   11.333%   $173.557   $173.56   $173.55   $173.60  
  Purchase #3 $119.56   11.267%   $133.0308   $133.03   $133.05   $133.00  
  Purchase #4 $238.91   5.187%   $251.3023   $251.30   $251.30   $251.30  
  Purchase #5 $27.89   13.726%   $31.7182   $31.72   $31.70   $31.70  
  Purchase #6 $236.64   5.570%   $249.8208   $249.82   $249.80   $249.80  
  Purchase #7 $132.26   7.225%   $141.8158   $141.82   $141.80   $141.80  
  7 purchase totals = $1,145.59       $1,227.9039   $1,227.91   $1,227.85   $1,227.90