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 $47.49   3.274%   $49.0448   $49.04   $49.05   $49.00  
  Purchase #2 $167.67   8.351%   $181.6721   $181.67   $181.65   $181.70  
  Purchase #3 $136.57   4.463%   $142.6651   $142.67   $142.65   $142.70  
  Purchase #4 $248.41   10.273%   $273.9292   $273.93   $273.95   $273.90  
  Purchase #5 $211.81   9.191%   $231.2775   $231.28   $231.30   $231.30  
  Purchase #6 $169.37   5.538%   $178.7497   $178.75   $178.75   $178.70  
  Purchase #7 $125.59   7.444%   $134.9389   $134.94   $134.95   $134.90  
  7 purchase totals = $1,106.91       $1,192.2773   $1,192.28   $1,192.30   $1,192.20