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 $212.75   6.456%   $226.4851   $226.49   $226.50   $226.50  
  Purchase #2 $238.74   3.451%   $246.9789   $246.98   $247.00   $247.00  
  Purchase #3 $23.40   4.870%   $24.5396   $24.54   $24.55   $24.50  
  Purchase #4 $186.67   8.798%   $203.0932   $203.09   $203.10   $203.10  
  Purchase #5 $130.29   5.720%   $137.7426   $137.74   $137.75   $137.70  
  Purchase #6 $95.59   6.289%   $101.6017   $101.60   $101.60   $101.60  
  Purchase #7 $71.35   3.516%   $73.8587   $73.86   $73.85   $73.90  
  7 purchase totals = $958.79       $1,014.2998   $1,014.30   $1,014.35   $1,014.30