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 $92.98   3.632%   $96.357   $96.36   $96.35   $96.40  
  Purchase #2 $106.81   11.500%   $119.0932   $119.09   $119.10   $119.10  
  Purchase #3 $42.46   8.429%   $46.039   $46.04   $46.05   $46.00  
  Purchase #4 $177.68   10.449%   $196.2458   $196.25   $196.25   $196.20  
  Purchase #5 $8.75   13.537%   $9.9345   $9.93   $9.95   $9.90  
  Purchase #6 $102.54   6.103%   $108.798   $108.80   $108.80   $108.80  
  Purchase #7 $195.77   10.177%   $215.6935   $215.69   $215.70   $215.70  
  7 purchase totals = $726.99       $792.1610   $792.16   $792.20   $792.10