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 $220.38   7.179%   $236.2011   $236.20   $236.20   $236.20  
  Purchase #2 $108.31   4.514%   $113.1991   $113.20   $113.20   $113.20  
  Purchase #3 $134.56   10.673%   $148.9216   $148.92   $148.90   $148.90  
  Purchase #4 $158.48   6.199%   $168.3042   $168.30   $168.30   $168.30  
  Purchase #5 $107.85   9.264%   $117.8412   $117.84   $117.85   $117.80  
  Purchase #6 $192.93   6.860%   $206.165   $206.17   $206.15   $206.20  
  Purchase #7 $62.40   6.252%   $66.3012   $66.30   $66.30   $66.30  
  7 purchase totals = $984.91       $1,056.9334   $1,056.93   $1,056.90   $1,056.90