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 $93.51   13.328%   $105.973   $105.97   $105.95   $106.00  
  Purchase #2 $136.55   12.210%   $153.2228   $153.22   $153.20   $153.20  
  Purchase #3 $142.39   6.586%   $151.7678   $151.77   $151.75   $151.80  
  Purchase #4 $25.53   8.706%   $27.7526   $27.75   $27.75   $27.80  
  Purchase #5 $47.74   7.711%   $51.4212   $51.42   $51.40   $51.40  
  Purchase #6 $9.74   5.250%   $10.2514   $10.25   $10.25   $10.30  
  Purchase #7 $240.34   7.684%   $258.8077   $258.81   $258.80   $258.80  
  7 purchase totals = $695.80       $759.1965   $759.19   $759.10   $759.30