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 $219.67   6.502%   $233.9529   $233.95   $233.95   $234.00  
  Purchase #2 $239.90   3.217%   $247.6176   $247.62   $247.60   $247.60  
  Purchase #3 $212.94   3.318%   $220.0053   $220.01   $220.00   $220.00  
  Purchase #4 $197.59   5.642%   $208.738   $208.74   $208.75   $208.70  
  Purchase #5 $237.78   4.736%   $249.0413   $249.04   $249.05   $249.00  
  Purchase #6 $14.49   6.117%   $15.3764   $15.38   $15.40   $15.40  
  Purchase #7 $224.31   4.663%   $234.7696   $234.77   $234.75   $234.80  
  7 purchase totals = $1,346.68       $1,409.5011   $1,409.51   $1,409.50   $1,409.50