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 $226.54   3.727%   $234.9831   $234.98   $235.00   $235.00  
  Purchase #2 $95.88   3.201%   $98.9491   $98.95   $98.95   $98.90  
  Purchase #3 $147.28   13.734%   $167.5074   $167.51   $167.50   $167.50  
  Purchase #4 $52.71   6.865%   $56.3285   $56.33   $56.35   $56.30  
  Purchase #5 $191.61   7.625%   $206.2203   $206.22   $206.20   $206.20  
  Purchase #6 $206.27   10.773%   $228.4915   $228.49   $228.50   $228.50  
  Purchase #7 $167.48   4.606%   $175.1941   $175.19   $175.20   $175.20  
  7 purchase totals = $1,087.77       $1,167.6740   $1,167.67   $1,167.70   $1,167.60