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 $82.29   12.635%   $92.6873   $92.69   $92.70   $92.70  
  Purchase #2 $238.72   11.506%   $266.1871   $266.19   $266.20   $266.20  
  Purchase #3 $12.70   6.132%   $13.4788   $13.48   $13.50   $13.50  
  Purchase #4 $140.51   10.571%   $155.3633   $155.36   $155.35   $155.40  
  Purchase #5 $49.55   4.766%   $51.9116   $51.91   $51.90   $51.90  
  Purchase #6 $162.33   4.312%   $169.3297   $169.33   $169.35   $169.30  
  Purchase #7 $182.88   9.173%   $199.6556   $199.66   $199.65   $199.70  
  7 purchase totals = $868.98       $948.6134   $948.62   $948.65   $948.70