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 $46.75   4.748%   $48.9697   $48.97   $48.95   $49.00  
  Purchase #2 $201.78   12.579%   $227.1619   $227.16   $227.15   $227.20  
  Purchase #3 $82.93   10.873%   $91.947   $91.95   $91.95   $91.90  
  Purchase #4 $235.48   10.203%   $259.506   $259.51   $259.50   $259.50  
  Purchase #5 $46.53   13.240%   $52.6906   $52.69   $52.70   $52.70  
  Purchase #6 $121.83   7.296%   $130.7187   $130.72   $130.70   $130.70  
  Purchase #7 $222.74   12.844%   $251.3487   $251.35   $251.35   $251.30  
  7 purchase totals = $958.04       $1,062.3426   $1,062.35   $1,062.30   $1,062.30