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 $185.55   6.157%   $196.9743   $196.97   $196.95   $197.00  
  Purchase #2 $51.35   4.334%   $53.5755   $53.58   $53.60   $53.60  
  Purchase #3 $12.81   12.553%   $14.418   $14.42   $14.40   $14.40  
  Purchase #4 $214.29   4.354%   $223.6202   $223.62   $223.60   $223.60  
  Purchase #5 $112.90   9.787%   $123.9495   $123.95   $123.95   $123.90  
  Purchase #6 $236.47   6.266%   $251.2872   $251.29   $251.30   $251.30  
  Purchase #7 $216.95   10.208%   $239.0963   $239.10   $239.10   $239.10  
  7 purchase totals = $1,030.32       $1,102.9210   $1,102.93   $1,102.90   $1,102.90