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 $228.75   7.524%   $245.9612   $245.96   $245.95   $246.00  
  Purchase #2 $229.91   10.298%   $253.5861   $253.59   $253.60   $253.60  
  Purchase #3 $232.89   3.497%   $241.0342   $241.03   $241.05   $241.00  
  Purchase #4 $82.74   11.807%   $92.5091   $92.51   $92.50   $92.50  
  Purchase #5 $61.85   10.178%   $68.1451   $68.15   $68.15   $68.10  
  Purchase #6 $213.49   9.141%   $233.0051   $233.01   $233.00   $233.00  
  Purchase #7 $19.41   10.512%   $21.4504   $21.45   $21.45   $21.50  
  7 purchase totals = $1,069.04       $1,155.6912   $1,155.70   $1,155.70   $1,155.70