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 $24.37   9.177%   $26.6064   $26.61   $26.60   $26.60  
  Purchase #2 $216.73   4.469%   $226.4157   $226.42   $226.40   $226.40  
  Purchase #3 $201.74   4.112%   $210.0355   $210.04   $210.05   $210.00  
  Purchase #4 $68.86   11.170%   $76.5517   $76.55   $76.55   $76.60  
  Purchase #5 $59.68   3.696%   $61.8858   $61.89   $61.90   $61.90  
  Purchase #6 $231.30   11.707%   $258.3783   $258.38   $258.40   $258.40  
  Purchase #7 $210.94   11.237%   $234.6433   $234.64   $234.65   $234.60  
  7 purchase totals = $1,013.62       $1,094.5167   $1,094.53   $1,094.55   $1,094.50