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 $67.85   9.305%   $74.1634   $74.16   $74.15   $74.20  
  Purchase #2 $238.28   10.537%   $263.3876   $263.39   $263.40   $263.40  
  Purchase #3 $12.86   5.277%   $13.5386   $13.54   $13.55   $13.50  
  Purchase #4 $96.69   13.504%   $109.747   $109.75   $109.75   $109.70  
  Purchase #5 $114.47   4.116%   $119.1816   $119.18   $119.20   $119.20  
  Purchase #6 $54.29   13.673%   $61.7131   $61.71   $61.70   $61.70  
  Purchase #7 $112.37   6.325%   $119.4774   $119.48   $119.50   $119.50  
  7 purchase totals = $696.81       $761.2087   $761.21   $761.25   $761.20