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 $195.71   4.375%   $204.2723   $204.27   $204.25   $204.30  
  Purchase #2 $243.63   9.109%   $265.8223   $265.82   $265.80   $265.80  
  Purchase #3 $75.36   5.391%   $79.4227   $79.42   $79.40   $79.40  
  Purchase #4 $169.60   7.680%   $182.6253   $182.63   $182.65   $182.60  
  Purchase #5 $187.46   9.720%   $205.6811   $205.68   $205.70   $205.70  
  Purchase #6 $165.84   10.486%   $183.23   $183.23   $183.25   $183.20  
  Purchase #7 $26.91   9.395%   $29.4382   $29.44   $29.45   $29.40  
  7 purchase totals = $1,064.51       $1,150.4919   $1,150.49   $1,150.50   $1,150.40