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 $243.71   9.159%   $266.0314   $266.03   $266.05   $266.00  
  Purchase #2 $62.90   7.119%   $67.3779   $67.38   $67.40   $67.40  
  Purchase #3 $203.29   11.378%   $226.4203   $226.42   $226.40   $226.40  
  Purchase #4 $94.39   9.405%   $103.2674   $103.27   $103.25   $103.30  
  Purchase #5 $88.42   8.839%   $96.2354   $96.24   $96.25   $96.20  
  Purchase #6 $230.81   13.680%   $262.3848   $262.38   $262.40   $262.40  
  Purchase #7 $68.39   7.120%   $73.2594   $73.26   $73.25   $73.30  
  7 purchase totals = $991.91       $1,094.9766   $1,094.98   $1,095.00   $1,095.00