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 $117.25   8.185%   $126.8469   $126.85   $126.85   $126.80  
  Purchase #2 $234.76   5.731%   $248.2141   $248.21   $248.20   $248.20  
  Purchase #3 $137.44   7.155%   $147.2738   $147.27   $147.25   $147.30  
  Purchase #4 $94.96   3.188%   $97.9873   $97.99   $98.00   $98.00  
  Purchase #5 $65.52   11.670%   $73.1662   $73.17   $73.15   $73.20  
  Purchase #6 $206.54   11.543%   $230.3809   $230.38   $230.40   $230.40  
  Purchase #7 $249.51   7.474%   $268.1584   $268.16   $268.15   $268.20  
  7 purchase totals = $1,105.98       $1,192.0276   $1,192.03   $1,192.00   $1,192.10