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 $14.85   8.242%   $16.0739   $16.07   $16.05   $16.10  
  Purchase #2 $162.52   8.479%   $176.3001   $176.30   $176.30   $176.30  
  Purchase #3 $75.59   8.390%   $81.932   $81.93   $81.95   $81.90  
  Purchase #4 $103.46   7.711%   $111.4378   $111.44   $111.45   $111.40  
  Purchase #5 $182.90   11.189%   $203.3647   $203.36   $203.35   $203.40  
  Purchase #6 $118.27   11.105%   $131.4039   $131.40   $131.40   $131.40  
  Purchase #7 $153.76   4.626%   $160.8729   $160.87   $160.85   $160.90  
  7 purchase totals = $811.35       $881.3853   $881.37   $881.35   $881.40