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 $108.85   9.279%   $118.9502   $118.95   $118.95   $119.00  
  Purchase #2 $240.81   3.369%   $248.9229   $248.92   $248.90   $248.90  
  Purchase #3 $28.84   5.854%   $30.5283   $30.53   $30.55   $30.50  
  Purchase #4 $21.58   13.301%   $24.4504   $24.45   $24.45   $24.50  
  Purchase #5 $103.86   4.263%   $108.2876   $108.29   $108.30   $108.30  
  Purchase #6 $183.39   13.269%   $207.724   $207.72   $207.70   $207.70  
  Purchase #7 $27.61   9.444%   $30.2175   $30.22   $30.20   $30.20  
  7 purchase totals = $714.94       $769.0809   $769.08   $769.05   $769.10