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 $41.28   13.707%   $46.9382   $46.94   $46.95   $46.90  
  Purchase #2 $205.80   4.387%   $214.8284   $214.83   $214.85   $214.80  
  Purchase #3 $93.35   11.646%   $104.2215   $104.22   $104.20   $104.20  
  Purchase #4 $58.57   13.748%   $66.6222   $66.62   $66.60   $66.60  
  Purchase #5 $59.75   11.150%   $66.4121   $66.41   $66.40   $66.40  
  Purchase #6 $201.58   3.773%   $209.1856   $209.19   $209.20   $209.20  
  Purchase #7 $46.70   5.605%   $49.3175   $49.32   $49.30   $49.30  
  7 purchase totals = $707.03       $757.5255   $757.53   $757.50   $757.40