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 $44.87   5.338%   $47.2652   $47.27   $47.25   $47.30  
  Purchase #2 $101.81   12.665%   $114.7042   $114.70   $114.70   $114.70  
  Purchase #3 $46.53   3.686%   $48.2451   $48.25   $48.25   $48.20  
  Purchase #4 $83.90   13.439%   $95.1753   $95.18   $95.20   $95.20  
  Purchase #5 $219.91   4.107%   $228.9417   $228.94   $228.95   $228.90  
  Purchase #6 $177.33   7.148%   $190.0055   $190.01   $190.00   $190.00  
  Purchase #7 $216.30   6.306%   $229.9399   $229.94   $229.95   $229.90  
  7 purchase totals = $890.65       $954.2769   $954.29   $954.30   $954.20