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 $44.69   4.356%   $46.6367   $46.64   $46.65   $46.60  
  Purchase #2 $195.27   8.440%   $211.7508   $211.75   $211.75   $211.80  
  Purchase #3 $165.99   5.671%   $175.4033   $175.40   $175.40   $175.40  
  Purchase #4 $143.76   5.419%   $151.5504   $151.55   $151.55   $151.60  
  Purchase #5 $10.59   7.113%   $11.3433   $11.34   $11.35   $11.30  
  Purchase #6 $62.59   3.643%   $64.8702   $64.87   $64.85   $64.90  
  Purchase #7 $159.62   10.409%   $176.2348   $176.23   $176.25   $176.20  
  7 purchase totals = $782.51       $837.7895   $837.78   $837.80   $837.80