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 $119.45   5.242%   $125.7116   $125.71   $125.70   $125.70  
  Purchase #2 $211.94   13.818%   $241.2259   $241.23   $241.25   $241.20  
  Purchase #3 $148.37   5.749%   $156.8998   $156.90   $156.90   $156.90  
  Purchase #4 $81.51   3.800%   $84.6074   $84.61   $84.60   $84.60  
  Purchase #5 $63.63   10.664%   $70.4155   $70.42   $70.40   $70.40  
  Purchase #6 $155.48   6.254%   $165.2037   $165.20   $165.20   $165.20  
  Purchase #7 $203.82   3.407%   $210.7641   $210.76   $210.75   $210.80  
  7 purchase totals = $984.20       $1,054.8280   $1,054.83   $1,054.80   $1,054.80