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 $73.37   5.305%   $77.2623   $77.26   $77.25   $77.30  
  Purchase #2 $232.88   11.793%   $260.3435   $260.34   $260.35   $260.30  
  Purchase #3 $179.57   3.768%   $186.3362   $186.34   $186.35   $186.30  
  Purchase #4 $68.83   9.596%   $75.4349   $75.43   $75.45   $75.40  
  Purchase #5 $121.78   12.660%   $137.1973   $137.20   $137.20   $137.20  
  Purchase #6 $190.70   4.804%   $199.8612   $199.86   $199.85   $199.90  
  Purchase #7 $79.66   8.206%   $86.1969   $86.20   $86.20   $86.20  
  7 purchase totals = $946.79       $1,022.6323   $1,022.63   $1,022.65   $1,022.60