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 $44.94   3.103%   $46.3345   $46.33   $46.35   $46.30  
  Purchase #2 $195.99   10.205%   $215.9908   $215.99   $216.00   $216.00  
  Purchase #3 $90.58   13.497%   $102.8056   $102.81   $102.80   $102.80  
  Purchase #4 $9.63   7.728%   $10.3742   $10.37   $10.35   $10.40  
  Purchase #5 $124.71   10.175%   $137.3992   $137.40   $137.40   $137.40  
  Purchase #6 $32.28   3.488%   $33.4059   $33.41   $33.40   $33.40  
  Purchase #7 $170.69   8.807%   $185.7227   $185.72   $185.70   $185.70  
  7 purchase totals = $668.82       $732.0329   $732.03   $732.00   $732.00