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 $58.95   9.801%   $64.7277   $64.73   $64.75   $64.70  
  Purchase #2 $242.93   4.713%   $254.3793   $254.38   $254.40   $254.40  
  Purchase #3 $188.68   11.277%   $209.9574   $209.96   $209.95   $210.00  
  Purchase #4 $224.88   3.734%   $233.277   $233.28   $233.30   $233.30  
  Purchase #5 $63.43   6.398%   $67.4883   $67.49   $67.50   $67.50  
  Purchase #6 $41.80   10.487%   $46.1836   $46.18   $46.20   $46.20  
  Purchase #7 $17.70   9.547%   $19.3898   $19.39   $19.40   $19.40  
  7 purchase totals = $838.37       $895.4031   $895.41   $895.50   $895.50