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 $63.42   13.744%   $72.1364   $72.14   $72.15   $72.10  
  Purchase #2 $222.71   10.495%   $246.0834   $246.08   $246.10   $246.10  
  Purchase #3 $177.78   6.649%   $189.6006   $189.60   $189.60   $189.60  
  Purchase #4 $136.76   10.682%   $151.3687   $151.37   $151.35   $151.40  
  Purchase #5 $199.91   13.507%   $226.9118   $226.91   $226.90   $226.90  
  Purchase #6 $179.54   11.224%   $199.6916   $199.69   $199.70   $199.70  
  Purchase #7 $223.57   10.412%   $246.8481   $246.85   $246.85   $246.80  
  7 purchase totals = $1,203.69       $1,332.6406   $1,332.64   $1,332.65   $1,332.60