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	$168.38	10.456%	$185.9858	$185.99	$186.00	$186.00
Purchase #2	$100.86	8.118%	$109.0478	$109.05	$109.05	$109.00
Purchase #3	$136.38	13.744%	$155.1241	$155.12	$155.10	$155.10
Purchase #4	$38.65	5.847%	$40.9099	$40.91	$40.90	$40.90
Purchase #5	$223.26	10.388%	$246.4522	$246.45	$246.45	$246.50
Purchase #6	$55.42	10.539%	$61.2607	$61.26	$61.25	$61.30
Purchase #7	$152.37	3.611%	$157.8721	$157.87	$157.85	$157.90
7 purchase totals =	$875.32		$956.6526	$956.65	$956.60	$956.70