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 $167.66   8.679%   $182.2112   $182.21   $182.20   $182.20  
  Purchase #2 $208.27   13.301%   $235.972   $235.97   $235.95   $236.00  
  Purchase #3 $117.95   12.468%   $132.656   $132.66   $132.65   $132.70  
  Purchase #4 $216.60   6.622%   $230.9433   $230.94   $230.95   $230.90  
  Purchase #5 $126.74   11.113%   $140.8246   $140.82   $140.80   $140.80  
  Purchase #6 $223.62   5.548%   $236.0264   $236.03   $236.05   $236.00  
  Purchase #7 $32.26   5.807%   $34.1333   $34.13   $34.15   $34.10  
  7 purchase totals = $1,093.10       $1,192.7668   $1,192.76   $1,192.75   $1,192.70