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 $89.39   5.445%   $94.2573   $94.26   $94.25   $94.30  
  Purchase #2 $119.83   3.207%   $123.6729   $123.67   $123.65   $123.70  
  Purchase #3 $86.42   3.443%   $89.3954   $89.40   $89.40   $89.40  
  Purchase #4 $234.51   4.677%   $245.478   $245.48   $245.50   $245.50  
  Purchase #5 $249.96   6.628%   $266.5273   $266.53   $266.55   $266.50  
  Purchase #6 $202.99   5.180%   $213.5049   $213.50   $213.50   $213.50  
  Purchase #7 $218.53   3.805%   $226.8451   $226.85   $226.85   $226.80  
  7 purchase totals = $1,201.63       $1,259.6809   $1,259.69   $1,259.70   $1,259.70