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	$104.81	4.121%	$109.1292	$109.13	$109.15	$109.10
Purchase #2	$126.36	3.259%	$130.4781	$130.48	$130.50	$130.50
Purchase #3	$202.38	10.137%	$222.8953	$222.90	$222.90	$222.90
Purchase #4	$250.68	9.763%	$275.1539	$275.15	$275.15	$275.20
Purchase #5	$221.95	3.668%	$230.0911	$230.09	$230.10	$230.10
Purchase #6	$224.70	6.303%	$238.8628	$238.86	$238.85	$238.90
Purchase #7	$148.35	4.363%	$154.8225	$154.82	$154.80	$154.80
7 purchase totals =	$1,279.23		$1,361.4329	$1,361.43	$1,361.45	$1,361.50