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 $216.65   8.872%   $235.8712   $235.87   $235.85   $235.90  
  Purchase #2 $125.45   9.767%   $137.7027   $137.70   $137.70   $137.70  
  Purchase #3 $206.47   8.676%   $224.3833   $224.38   $224.40   $224.40  
  Purchase #4 $241.84   12.531%   $272.145   $272.15   $272.15   $272.10  
  Purchase #5 $232.68   6.188%   $247.0782   $247.08   $247.10   $247.10  
  Purchase #6 $87.34   9.407%   $95.5561   $95.56   $95.55   $95.60  
  Purchase #7 $244.48   4.473%   $255.4156   $255.42   $255.40   $255.40  
  7 purchase totals = $1,354.91       $1,468.1521   $1,468.16   $1,468.15   $1,468.20