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	$210.60	4.413%	$219.8938	$219.89	$219.90	$219.90
Purchase #2	$212.80	8.245%	$230.3454	$230.35	$230.35	$230.30
Purchase #3	$136.59	3.326%	$141.133	$141.13	$141.15	$141.10
Purchase #4	$174.26	7.150%	$186.7196	$186.72	$186.70	$186.70
Purchase #5	$166.73	3.455%	$172.4905	$172.49	$172.50	$172.50
Purchase #6	$151.50	13.806%	$172.4161	$172.42	$172.40	$172.40
Purchase #7	$21.65	8.738%	$23.5418	$23.54	$23.55	$23.50
7 purchase totals =	$1,074.13		$1,146.5402	$1,146.54	$1,146.55	$1,146.40