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 $71.35   6.668%   $76.1076   $76.11   $76.10   $76.10  
  Purchase #2 $215.90   3.479%   $223.4112   $223.41   $223.40   $223.40  
  Purchase #3 $46.40   12.451%   $52.1773   $52.18   $52.20   $52.20  
  Purchase #4 $18.37   4.632%   $19.2209   $19.22   $19.20   $19.20  
  Purchase #5 $228.77   7.214%   $245.2735   $245.27   $245.25   $245.30  
  Purchase #6 $132.86   10.365%   $146.6309   $146.63   $146.65   $146.60  
  Purchase #7 $246.49   5.373%   $259.7339   $259.73   $259.75   $259.70  
  7 purchase totals = $960.14       $1,022.5553   $1,022.55   $1,022.55   $1,022.50