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 $218.65   11.800%   $244.4507   $244.45   $244.45   $244.50  
  Purchase #2 $38.92   5.381%   $41.0143   $41.01   $41.00   $41.00  
  Purchase #3 $133.50   11.388%   $148.703   $148.70   $148.70   $148.70  
  Purchase #4 $186.70   7.635%   $200.9545   $200.95   $200.95   $201.00  
  Purchase #5 $66.85   8.871%   $72.7803   $72.78   $72.80   $72.80  
  Purchase #6 $179.59   5.664%   $189.762   $189.76   $189.75   $189.80  
  Purchase #7 $133.68   4.664%   $139.9148   $139.91   $139.90   $139.90  
  7 purchase totals = $957.89       $1,037.5796   $1,037.56   $1,037.55   $1,037.70