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 $61.26   4.197%   $63.8311   $63.83   $63.85   $63.80  
  Purchase #2 $241.84   5.512%   $255.1702   $255.17   $255.15   $255.20  
  Purchase #3 $233.85   6.205%   $248.3604   $248.36   $248.35   $248.40  
  Purchase #4 $164.47   5.424%   $173.3909   $173.39   $173.40   $173.40  
  Purchase #5 $80.46   7.583%   $86.5613   $86.56   $86.55   $86.60  
  Purchase #6 $105.84   4.674%   $110.787   $110.79   $110.80   $110.80  
  Purchase #7 $125.82   8.225%   $136.1687   $136.17   $136.15   $136.20  
  7 purchase totals = $1,013.54       $1,074.2696   $1,074.27   $1,074.25   $1,074.40