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 $192.48   11.362%   $214.3496   $214.35   $214.35   $214.30  
  Purchase #2 $97.93   4.408%   $102.2468   $102.25   $102.25   $102.20  
  Purchase #3 $53.42   12.571%   $60.1354   $60.14   $60.15   $60.10  
  Purchase #4 $231.47   12.771%   $261.031   $261.03   $261.05   $261.00  
  Purchase #5 $248.57   6.656%   $265.1148   $265.11   $265.10   $265.10  
  Purchase #6 $155.86   8.436%   $169.0083   $169.01   $169.00   $169.00  
  Purchase #7 $52.49   11.127%   $58.3306   $58.33   $58.35   $58.30  
  7 purchase totals = $1,032.22       $1,130.2165   $1,130.22   $1,130.25   $1,130.00