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 $66.53   10.432%   $73.4704   $73.47   $73.45   $73.50  
  Purchase #2 $206.77   4.707%   $216.5027   $216.50   $216.50   $216.50  
  Purchase #3 $55.57   4.432%   $58.0329   $58.03   $58.05   $58.00  
  Purchase #4 $185.42   10.633%   $205.1357   $205.14   $205.15   $205.10  
  Purchase #5 $106.70   3.229%   $110.1453   $110.15   $110.15   $110.10  
  Purchase #6 $164.38   3.790%   $170.61   $170.61   $170.60   $170.60  
  Purchase #7 $88.78   3.756%   $92.1146   $92.11   $92.10   $92.10  
  7 purchase totals = $874.15       $926.0116   $926.01   $926.00   $925.90