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 $209.66   11.501%   $233.773   $233.77   $233.75   $233.80  
  Purchase #2 $212.56   8.614%   $230.8699   $230.87   $230.85   $230.90  
  Purchase #3 $231.34   9.282%   $252.813   $252.81   $252.80   $252.80  
  Purchase #4 $207.49   12.796%   $234.0404   $234.04   $234.05   $234.00  
  Purchase #5 $118.42   5.619%   $125.074   $125.07   $125.05   $125.10  
  Purchase #6 $92.50   9.498%   $101.2857   $101.29   $101.30   $101.30  
  Purchase #7 $146.44   5.500%   $154.4942   $154.49   $154.50   $154.50  
  7 purchase totals = $1,218.41       $1,332.3502   $1,332.34   $1,332.30   $1,332.40