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 $143.94   5.537%   $151.91   $151.91   $151.90   $151.90  
  Purchase #2 $183.41   6.367%   $195.0877   $195.09   $195.10   $195.10  
  Purchase #3 $180.52   10.765%   $199.953   $199.95   $199.95   $200.00  
  Purchase #4 $26.86   10.838%   $29.7711   $29.77   $29.75   $29.80  
  Purchase #5 $214.99   6.381%   $228.7085   $228.71   $228.70   $228.70  
  Purchase #6 $41.71   4.115%   $43.4264   $43.43   $43.45   $43.40  
  Purchase #7 $93.44   5.754%   $98.8165   $98.82   $98.80   $98.80  
  7 purchase totals = $884.87       $947.6732   $947.68   $947.65   $947.70