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 $224.81   5.294%   $236.7114   $236.71   $236.70   $236.70  
  Purchase #2 $243.35   7.872%   $262.5065   $262.51   $262.50   $262.50  
  Purchase #3 $63.26   10.792%   $70.087   $70.09   $70.10   $70.10  
  Purchase #4 $87.92   5.590%   $92.8347   $92.83   $92.85   $92.80  
  Purchase #5 $126.60   11.383%   $141.0109   $141.01   $141.00   $141.00  
  Purchase #6 $11.54   3.793%   $11.9777   $11.98   $12.00   $12.00  
  Purchase #7 $246.82   13.765%   $280.7948   $280.79   $280.80   $280.80  
  7 purchase totals = $1,004.30       $1,095.9230   $1,095.92   $1,095.95   $1,095.90