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 $195.41   6.569%   $208.2465   $208.25   $208.25   $208.20  
  Purchase #2 $63.97   6.342%   $68.027   $68.03   $68.05   $68.00  
  Purchase #3 $210.83   4.814%   $220.9794   $220.98   $221.00   $221.00  
  Purchase #4 $237.87   5.444%   $250.8196   $250.82   $250.80   $250.80  
  Purchase #5 $136.56   5.584%   $144.1855   $144.19   $144.20   $144.20  
  Purchase #6 $222.58   9.454%   $243.6227   $243.62   $243.60   $243.60  
  Purchase #7 $136.29   11.516%   $151.9852   $151.99   $152.00   $152.00  
  7 purchase totals = $1,203.51       $1,287.8659   $1,287.88   $1,287.90   $1,287.80