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 $44.26   9.269%   $48.3625   $48.36   $48.35   $48.40  
  Purchase #2 $196.42   11.362%   $218.7372   $218.74   $218.75   $218.70  
  Purchase #3 $156.26   11.593%   $174.3752   $174.38   $174.40   $174.40  
  Purchase #4 $179.87   9.842%   $197.5728   $197.57   $197.55   $197.60  
  Purchase #5 $157.83   10.523%   $174.4385   $174.44   $174.45   $174.40  
  Purchase #6 $151.99   11.446%   $169.3868   $169.39   $169.40   $169.40  
  Purchase #7 $163.36   9.770%   $179.3203   $179.32   $179.30   $179.30  
  7 purchase totals = $1,049.99       $1,162.1933   $1,162.20   $1,162.20   $1,162.20