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 $227.35   6.200%   $241.4457   $241.45   $241.45   $241.40  
  Purchase #2 $59.90   12.429%   $67.345   $67.35   $67.35   $67.30  
  Purchase #3 $13.25   5.247%   $13.9452   $13.95   $13.95   $13.90  
  Purchase #4 $191.96   5.203%   $201.9477   $201.95   $201.95   $201.90  
  Purchase #5 $84.27   10.545%   $93.1563   $93.16   $93.15   $93.20  
  Purchase #6 $142.75   4.304%   $148.894   $148.89   $148.90   $148.90  
  Purchase #7 $235.82   5.117%   $247.8869   $247.89   $247.90   $247.90  
  7 purchase totals = $955.30       $1,014.6208   $1,014.64   $1,014.65   $1,014.50