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 $187.32   7.674%   $201.6949   $201.69   $201.70   $201.70  
  Purchase #2 $212.70   3.592%   $220.3402   $220.34   $220.35   $220.30  
  Purchase #3 $158.98   8.698%   $172.8081   $172.81   $172.80   $172.80  
  Purchase #4 $245.87   13.380%   $278.7674   $278.77   $278.75   $278.80  
  Purchase #5 $98.78   13.749%   $112.3613   $112.36   $112.35   $112.40  
  Purchase #6 $242.40   4.703%   $253.8001   $253.80   $253.80   $253.80  
  Purchase #7 $153.68   13.756%   $174.8202   $174.82   $174.80   $174.80  
  7 purchase totals = $1,299.73       $1,414.5922   $1,414.59   $1,414.55   $1,414.60