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 $86.92   10.749%   $96.263   $96.26   $96.25   $96.30  
  Purchase #2 $104.30   11.646%   $116.4468   $116.45   $116.45   $116.40  
  Purchase #3 $234.32   8.425%   $254.0615   $254.06   $254.05   $254.10  
  Purchase #4 $146.37   3.519%   $151.5208   $151.52   $151.50   $151.50  
  Purchase #5 $42.43   10.306%   $46.8028   $46.80   $46.80   $46.80  
  Purchase #6 $230.45   10.167%   $253.8799   $253.88   $253.90   $253.90  
  Purchase #7 $206.79   8.815%   $225.0185   $225.02   $225.00   $225.00  
  7 purchase totals = $1,051.58       $1,143.9933   $1,143.99   $1,143.95   $1,144.00