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 $175.96   10.480%   $194.4006   $194.40   $194.40   $194.40  
  Purchase #2 $236.43   6.738%   $252.3607   $252.36   $252.35   $252.40  
  Purchase #3 $18.26   11.406%   $20.3427   $20.34   $20.35   $20.30  
  Purchase #4 $84.79   8.863%   $92.3049   $92.30   $92.30   $92.30  
  Purchase #5 $101.26   6.550%   $107.8925   $107.89   $107.90   $107.90  
  Purchase #6 $217.52   11.754%   $243.0873   $243.09   $243.10   $243.10  
  Purchase #7 $243.41   7.768%   $262.3181   $262.32   $262.30   $262.30  
  7 purchase totals = $1,077.63       $1,172.7068   $1,172.70   $1,172.70   $1,172.70