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 $69.91   9.709%   $76.6976   $76.70   $76.70   $76.70  
  Purchase #2 $33.78   6.869%   $36.1003   $36.10   $36.10   $36.10  
  Purchase #3 $190.33   13.580%   $216.1768   $216.18   $216.20   $216.20  
  Purchase #4 $69.81   4.428%   $72.9012   $72.90   $72.90   $72.90  
  Purchase #5 $234.32   4.365%   $244.5481   $244.55   $244.55   $244.50  
  Purchase #6 $84.77   8.642%   $92.0958   $92.10   $92.10   $92.10  
  Purchase #7 $184.35   5.411%   $194.3252   $194.33   $194.35   $194.30  
  7 purchase totals = $867.27       $932.8450   $932.86   $932.90   $932.80