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 $195.57   10.569%   $216.2398   $216.24   $216.25   $216.20  
  Purchase #2 $96.83   11.555%   $108.0187   $108.02   $108.00   $108.00  
  Purchase #3 $169.32   7.264%   $181.6194   $181.62   $181.60   $181.60  
  Purchase #4 $224.55   7.664%   $241.7595   $241.76   $241.75   $241.80  
  Purchase #5 $197.75   8.504%   $214.5667   $214.57   $214.55   $214.60  
  Purchase #6 $151.56   11.104%   $168.3892   $168.39   $168.40   $168.40  
  Purchase #7 $140.66   7.312%   $150.9451   $150.95   $150.95   $150.90  
  7 purchase totals = $1,176.24       $1,281.5384   $1,281.55   $1,281.50   $1,281.50