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 $208.81   7.478%   $224.4248   $224.42   $224.40   $224.40  
  Purchase #2 $11.36   7.116%   $12.1684   $12.17   $12.15   $12.20  
  Purchase #3 $165.53   4.860%   $173.5748   $173.57   $173.55   $173.60  
  Purchase #4 $183.41   6.299%   $194.963   $194.96   $194.95   $195.00  
  Purchase #5 $228.82   7.475%   $245.9243   $245.92   $245.90   $245.90  
  Purchase #6 $5.95   5.403%   $6.2715   $6.27   $6.25   $6.30  
  Purchase #7 $33.64   13.108%   $38.0495   $38.05   $38.05   $38.00  
  7 purchase totals = $837.52       $895.3763   $895.36   $895.25   $895.40