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 $240.47   5.462%   $253.6045   $253.60   $253.60   $253.60  
  Purchase #2 $216.32   4.723%   $226.5368   $226.54   $226.55   $226.50  
  Purchase #3 $247.92   11.703%   $276.9341   $276.93   $276.95   $276.90  
  Purchase #4 $234.55   3.818%   $243.5051   $243.51   $243.50   $243.50  
  Purchase #5 $231.83   5.669%   $244.9724   $244.97   $244.95   $245.00  
  Purchase #6 $239.68   11.205%   $266.5361   $266.54   $266.55   $266.50  
  Purchase #7 $48.55   4.353%   $50.6634   $50.66   $50.65   $50.70  
  7 purchase totals = $1,459.32       $1,562.7524   $1,562.75   $1,562.75   $1,562.70