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 $195.99   13.722%   $222.8837   $222.88   $222.90   $222.90  
  Purchase #2 $54.28   11.606%   $60.5797   $60.58   $60.60   $60.60  
  Purchase #3 $210.73   10.152%   $232.1233   $232.12   $232.10   $232.10  
  Purchase #4 $48.35   12.303%   $54.2985   $54.30   $54.30   $54.30  
  Purchase #5 $110.33   10.827%   $122.2754   $122.28   $122.30   $122.30  
  Purchase #6 $247.62   3.397%   $256.0317   $256.03   $256.05   $256.00  
  Purchase #7 $58.38   6.215%   $62.0083   $62.01   $62.00   $62.00  
  7 purchase totals = $925.68       $1,010.2006   $1,010.20   $1,010.25   $1,010.20