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	$220.34	3.636%	$228.3516	$228.35	$228.35	$228.40
Purchase #2	$67.90	3.198%	$70.0714	$70.07	$70.05	$70.10
Purchase #3	$222.71	6.195%	$236.5069	$236.51	$236.50	$236.50
Purchase #4	$149.69	11.350%	$166.6798	$166.68	$166.70	$166.70
Purchase #5	$32.87	12.130%	$36.8571	$36.86	$36.85	$36.90
Purchase #6	$164.89	4.853%	$172.8921	$172.89	$172.90	$172.90
Purchase #7	$128.85	11.579%	$143.7695	$143.77	$143.75	$143.80
7 purchase totals =	$987.25		$1,055.1284	$1,055.13	$1,055.10	$1,055.30