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 $48.91   10.301%   $53.9482   $53.95   $53.95   $53.90  
  Purchase #2 $146.93   4.574%   $153.6506   $153.65   $153.65   $153.70  
  Purchase #3 $139.81   5.818%   $147.9441   $147.94   $147.95   $147.90  
  Purchase #4 $155.37   6.301%   $165.1599   $165.16   $165.15   $165.20  
  Purchase #5 $213.73   3.514%   $221.2405   $221.24   $221.25   $221.20  
  Purchase #6 $217.40   11.703%   $242.8423   $242.84   $242.85   $242.80  
  Purchase #7 $232.73   6.526%   $247.918   $247.92   $247.90   $247.90  
  7 purchase totals = $1,154.88       $1,232.7036   $1,232.70   $1,232.70   $1,232.60