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 $91.66   11.202%   $101.9278   $101.93   $101.95   $101.90  
  Purchase #2 $65.42   10.503%   $72.2911   $72.29   $72.30   $72.30  
  Purchase #3 $113.67   8.580%   $123.4229   $123.42   $123.40   $123.40  
  Purchase #4 $138.86   9.186%   $151.6157   $151.62   $151.60   $151.60  
  Purchase #5 $193.37   10.796%   $214.2462   $214.25   $214.25   $214.20  
  Purchase #6 $186.33   3.833%   $193.472   $193.47   $193.45   $193.50  
  Purchase #7 $167.95   11.710%   $187.6169   $187.62   $187.60   $187.60  
  7 purchase totals = $957.26       $1,044.5926   $1,044.60   $1,044.55   $1,044.50