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 $214.55   7.675%   $231.0167   $231.02   $231.00   $231.00  
  Purchase #2 $228.37   8.695%   $248.2268   $248.23   $248.25   $248.20  
  Purchase #3 $48.87   3.139%   $50.404   $50.40   $50.40   $50.40  
  Purchase #4 $157.99   5.140%   $166.1107   $166.11   $166.10   $166.10  
  Purchase #5 $42.47   5.161%   $44.6619   $44.66   $44.65   $44.70  
  Purchase #6 $59.34   8.330%   $64.283   $64.28   $64.30   $64.30  
  Purchase #7 $19.70   6.715%   $21.0229   $21.02   $21.00   $21.00  
  7 purchase totals = $771.29       $825.7260   $825.72   $825.70   $825.70