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 $41.26   11.502%   $46.0057   $46.01   $46.00   $46.00  
  Purchase #2 $227.89   10.251%   $251.251   $251.25   $251.25   $251.30  
  Purchase #3 $17.66   10.627%   $19.5367   $19.54   $19.55   $19.50  
  Purchase #4 $169.62   8.704%   $184.3837   $184.38   $184.40   $184.40  
  Purchase #5 $239.64   10.416%   $264.6009   $264.60   $264.60   $264.60  
  Purchase #6 $244.42   8.784%   $265.8899   $265.89   $265.90   $265.90  
  Purchase #7 $170.99   9.526%   $187.2785   $187.28   $187.30   $187.30  
  7 purchase totals = $1,111.48       $1,218.9464   $1,218.95   $1,219.00   $1,219.00