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 $73.94   4.462%   $77.2392   $77.24   $77.25   $77.20  
  Purchase #2 $185.34   11.534%   $206.7171   $206.72   $206.70   $206.70  
  Purchase #3 $91.75   8.377%   $99.4359   $99.44   $99.45   $99.40  
  Purchase #4 $96.31   9.481%   $105.4412   $105.44   $105.45   $105.40  
  Purchase #5 $166.80   10.291%   $183.9654   $183.97   $183.95   $184.00  
  Purchase #6 $108.75   6.142%   $115.4294   $115.43   $115.45   $115.40  
  Purchase #7 $246.98   5.481%   $260.517   $260.52   $260.50   $260.50  
  7 purchase totals = $969.87       $1,048.7452   $1,048.76   $1,048.75   $1,048.60