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 $211.57   10.860%   $234.5465   $234.55   $234.55   $234.50  
  Purchase #2 $98.92   3.105%   $101.9915   $101.99   $102.00   $102.00  
  Purchase #3 $56.96   10.149%   $62.7409   $62.74   $62.75   $62.70  
  Purchase #4 $5.83   3.380%   $6.0271   $6.03   $6.05   $6.00  
  Purchase #5 $100.60   3.176%   $103.7951   $103.80   $103.80   $103.80  
  Purchase #6 $120.42   5.294%   $126.795   $126.80   $126.80   $126.80  
  Purchase #7 $136.32   10.212%   $150.241   $150.24   $150.25   $150.20  
  7 purchase totals = $730.62       $786.1371   $786.15   $786.20   $786.00