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 $118.46   6.394%   $126.0343   $126.03   $126.05   $126.00  
  Purchase #2 $246.97   7.330%   $265.0729   $265.07   $265.05   $265.10  
  Purchase #3 $42.92   8.646%   $46.6309   $46.63   $46.65   $46.60  
  Purchase #4 $79.69   5.322%   $83.9311   $83.93   $83.95   $83.90  
  Purchase #5 $90.91   9.598%   $99.6355   $99.64   $99.65   $99.60  
  Purchase #6 $224.38   13.405%   $254.4581   $254.46   $254.45   $254.50  
  Purchase #7 $214.73   13.657%   $244.0557   $244.06   $244.05   $244.10  
  7 purchase totals = $1,018.06       $1,119.8185   $1,119.82   $1,119.85   $1,119.80