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 $202.74   5.577%   $214.0468   $214.05   $214.05   $214.00  
  Purchase #2 $9.26   10.569%   $10.2387   $10.24   $10.25   $10.20  
  Purchase #3 $194.84   5.475%   $205.5075   $205.51   $205.50   $205.50  
  Purchase #4 $167.81   10.871%   $186.0526   $186.05   $186.05   $186.10  
  Purchase #5 $71.65   3.535%   $74.1828   $74.18   $74.20   $74.20  
  Purchase #6 $187.42   4.839%   $196.4893   $196.49   $196.50   $196.50  
  Purchase #7 $129.73   3.503%   $134.2744   $134.27   $134.25   $134.30  
  7 purchase totals = $963.45       $1,020.7921   $1,020.79   $1,020.80   $1,020.80