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 $48.74   7.690%   $52.4881   $52.49   $52.50   $52.50  
  Purchase #2 $223.41   9.340%   $244.2765   $244.28   $244.30   $244.30  
  Purchase #3 $222.68   11.837%   $249.0386   $249.04   $249.05   $249.00  
  Purchase #4 $179.58   6.325%   $190.9384   $190.94   $190.95   $190.90  
  Purchase #5 $84.81   3.394%   $87.6885   $87.69   $87.70   $87.70  
  Purchase #6 $239.63   4.601%   $250.6554   $250.66   $250.65   $250.70  
  Purchase #7 $120.38   5.299%   $126.7589   $126.76   $126.75   $126.80  
  7 purchase totals = $1,119.23       $1,201.8444   $1,201.86   $1,201.90   $1,201.90