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 $194.68   3.824%   $202.1246   $202.12   $202.10   $202.10  
  Purchase #2 $204.54   3.328%   $211.3471   $211.35   $211.35   $211.30  
  Purchase #3 $118.64   4.637%   $124.1413   $124.14   $124.15   $124.10  
  Purchase #4 $62.88   10.571%   $69.527   $69.53   $69.55   $69.50  
  Purchase #5 $112.60   9.438%   $123.2272   $123.23   $123.25   $123.20  
  Purchase #6 $100.55   13.725%   $114.3505   $114.35   $114.35   $114.40  
  Purchase #7 $205.44   5.606%   $216.957   $216.96   $216.95   $217.00  
  7 purchase totals = $999.33       $1,061.6747   $1,061.68   $1,061.70   $1,061.60