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 $44.50   4.153%   $46.3481   $46.35   $46.35   $46.30  
  Purchase #2 $52.34   11.818%   $58.5255   $58.53   $58.55   $58.50  
  Purchase #3 $228.87   9.179%   $249.878   $249.88   $249.90   $249.90  
  Purchase #4 $198.94   4.430%   $207.753   $207.75   $207.75   $207.80  
  Purchase #5 $108.30   10.224%   $119.3726   $119.37   $119.35   $119.40  
  Purchase #6 $144.37   11.784%   $161.3826   $161.38   $161.40   $161.40  
  Purchase #7 $164.84   10.203%   $181.6586   $181.66   $181.65   $181.70  
  7 purchase totals = $942.16       $1,024.9184   $1,024.92   $1,024.95   $1,025.00