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 $55.63   10.396%   $61.4133   $61.41   $61.40   $61.40  
  Purchase #2 $244.28   5.594%   $257.945   $257.95   $257.95   $257.90  
  Purchase #3 $119.50   10.493%   $132.0391   $132.04   $132.05   $132.00  
  Purchase #4 $154.44   4.760%   $161.7913   $161.79   $161.80   $161.80  
  Purchase #5 $197.49   11.243%   $219.6938   $219.69   $219.70   $219.70  
  Purchase #6 $88.90   9.216%   $97.093   $97.09   $97.10   $97.10  
  Purchase #7 $70.48   7.747%   $75.9401   $75.94   $75.95   $75.90  
  7 purchase totals = $930.72       $1,005.9156   $1,005.91   $1,005.95   $1,005.80