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 $113.52   4.491%   $118.6182   $118.62   $118.60   $118.60  
  Purchase #2 $149.55   3.302%   $154.4881   $154.49   $154.50   $154.50  
  Purchase #3 $95.73   10.305%   $105.595   $105.60   $105.60   $105.60  
  Purchase #4 $228.56   7.402%   $245.478   $245.48   $245.50   $245.50  
  Purchase #5 $70.71   12.446%   $79.5106   $79.51   $79.50   $79.50  
  Purchase #6 $243.63   10.389%   $268.9407   $268.94   $268.95   $268.90  
  Purchase #7 $193.41   11.139%   $214.9539   $214.95   $214.95   $215.00  
  7 purchase totals = $1,095.11       $1,187.5845   $1,187.59   $1,187.60   $1,187.60