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	$104.72	11.285%	$116.5377	$116.54	$116.55	$116.50
Purchase #2	$214.71	11.148%	$238.6459	$238.65	$238.65	$238.60
Purchase #3	$143.54	7.226%	$153.9122	$153.91	$153.90	$153.90
Purchase #4	$230.86	3.479%	$238.8916	$238.89	$238.90	$238.90
Purchase #5	$22.57	3.263%	$23.3065	$23.31	$23.30	$23.30
Purchase #6	$101.75	13.593%	$115.5809	$115.58	$115.60	$115.60
Purchase #7	$157.27	10.810%	$174.2709	$174.27	$174.25	$174.30
7 purchase totals =	$975.42		$1,061.1457	$1,061.15	$1,061.15	$1,061.10