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 $173.71   12.811%   $195.964   $195.96   $195.95   $196.00  
  Purchase #2 $152.82   10.439%   $168.7729   $168.77   $168.75   $168.80  
  Purchase #3 $196.86   4.659%   $206.0317   $206.03   $206.05   $206.00  
  Purchase #4 $195.62   13.349%   $221.7333   $221.73   $221.75   $221.70  
  Purchase #5 $81.59   13.708%   $92.7744   $92.77   $92.75   $92.80  
  Purchase #6 $207.65   10.865%   $230.2112   $230.21   $230.20   $230.20  
  Purchase #7 $75.57   4.399%   $78.8943   $78.89   $78.90   $78.90  
  7 purchase totals = $1,083.82       $1,194.3818   $1,194.36   $1,194.35   $1,194.40