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 $70.95   7.411%   $76.2081   $76.21   $76.20   $76.20  
  Purchase #2 $215.77   4.738%   $225.9932   $225.99   $226.00   $226.00  
  Purchase #3 $14.92   8.743%   $16.2245   $16.22   $16.20   $16.20  
  Purchase #4 $58.31   11.605%   $65.0769   $65.08   $65.10   $65.10  
  Purchase #5 $59.79   5.321%   $62.9714   $62.97   $62.95   $63.00  
  Purchase #6 $127.30   3.169%   $131.3341   $131.33   $131.35   $131.30  
  Purchase #7 $87.33   12.764%   $98.4768   $98.48   $98.50   $98.50  
  7 purchase totals = $634.37       $676.2850   $676.28   $676.30   $676.30