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 $110.62   5.622%   $116.8391   $116.84   $116.85   $116.80  
  Purchase #2 $70.65   5.267%   $74.3711   $74.37   $74.35   $74.40  
  Purchase #3 $224.55   3.748%   $232.9661   $232.97   $232.95   $233.00  
  Purchase #4 $24.33   7.688%   $26.2005   $26.20   $26.20   $26.20  
  Purchase #5 $178.98   11.775%   $200.0549   $200.05   $200.05   $200.10  
  Purchase #6 $59.26   7.710%   $63.8289   $63.83   $63.85   $63.80  
  Purchase #7 $205.95   10.314%   $227.1917   $227.19   $227.20   $227.20  
  7 purchase totals = $874.34       $941.4523   $941.45   $941.45   $941.50