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 $208.83   9.562%   $228.7983   $228.80   $228.80   $228.80  
  Purchase #2 $188.73   4.276%   $196.8001   $196.80   $196.80   $196.80  
  Purchase #3 $17.62   5.392%   $18.5701   $18.57   $18.55   $18.60  
  Purchase #4 $30.64   8.352%   $33.1991   $33.20   $33.20   $33.20  
  Purchase #5 $43.41   6.249%   $46.1227   $46.12   $46.10   $46.10  
  Purchase #6 $147.43   13.213%   $166.9099   $166.91   $166.90   $166.90  
  Purchase #7 $207.71   3.430%   $214.8345   $214.83   $214.85   $214.80  
  7 purchase totals = $844.37       $905.2347   $905.23   $905.20   $905.20