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 $41.59   7.441%   $44.6847   $44.68   $44.70   $44.70  
  Purchase #2 $194.39   10.780%   $215.3452   $215.35   $215.35   $215.30  
  Purchase #3 $166.62   7.518%   $179.1465   $179.15   $179.15   $179.10  
  Purchase #4 $82.93   4.343%   $86.5316   $86.53   $86.55   $86.50  
  Purchase #5 $158.37   9.317%   $173.1253   $173.13   $173.15   $173.10  
  Purchase #6 $157.43   4.863%   $165.0858   $165.09   $165.10   $165.10  
  Purchase #7 $62.61   12.811%   $70.631   $70.63   $70.65   $70.60  
  7 purchase totals = $863.94       $934.5501   $934.56   $934.65   $934.40