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 $65.38   5.699%   $69.106   $69.11   $69.10   $69.10  
  Purchase #2 $168.37   3.151%   $173.6753   $173.68   $173.70   $173.70  
  Purchase #3 $99.48   12.659%   $112.0732   $112.07   $112.05   $112.10  
  Purchase #4 $141.54   9.688%   $155.2524   $155.25   $155.25   $155.30  
  Purchase #5 $206.50   7.102%   $221.1656   $221.17   $221.15   $221.20  
  Purchase #6 $59.82   4.742%   $62.6567   $62.66   $62.65   $62.70  
  Purchase #7 $12.50   8.707%   $13.5884   $13.59   $13.60   $13.60  
  7 purchase totals = $753.59       $807.5176   $807.53   $807.50   $807.70