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 $58.37   5.318%   $61.4741   $61.47   $61.45   $61.50  
  Purchase #2 $221.98   10.482%   $245.2479   $245.25   $245.25   $245.20  
  Purchase #3 $203.60   3.480%   $210.6853   $210.69   $210.70   $210.70  
  Purchase #4 $232.61   6.402%   $247.5017   $247.50   $247.50   $247.50  
  Purchase #5 $9.30   12.250%   $10.4393   $10.44   $10.45   $10.40  
  Purchase #6 $74.48   3.832%   $77.3341   $77.33   $77.35   $77.30  
  Purchase #7 $167.96   4.782%   $175.9918   $175.99   $176.00   $176.00  
  7 purchase totals = $968.30       $1,028.6742   $1,028.67   $1,028.70   $1,028.60