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 $215.32   9.817%   $236.458   $236.46   $236.45   $236.50  
  Purchase #2 $173.75   9.789%   $190.7584   $190.76   $190.75   $190.80  
  Purchase #3 $126.57   4.823%   $132.6745   $132.67   $132.65   $132.70  
  Purchase #4 $197.38   5.361%   $207.9615   $207.96   $207.95   $208.00  
  Purchase #5 $78.27   6.484%   $83.345   $83.35   $83.35   $83.30  
  Purchase #6 $89.33   9.543%   $97.8548   $97.85   $97.85   $97.90  
  Purchase #7 $172.42   5.189%   $181.3669   $181.37   $181.35   $181.40  
  7 purchase totals = $1,053.04       $1,130.4191   $1,130.42   $1,130.35   $1,130.60