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	$50.47	8.433%	$54.7261	$54.73	$54.75	$54.70
Purchase #2	$201.28	10.760%	$222.9377	$222.94	$222.95	$222.90
Purchase #3	$235.76	6.831%	$251.8648	$251.86	$251.85	$251.90
Purchase #4	$77.99	12.133%	$87.4525	$87.45	$87.45	$87.50
Purchase #5	$161.77	3.425%	$167.3106	$167.31	$167.30	$167.30
Purchase #6	$206.64	3.704%	$214.2939	$214.29	$214.30	$214.30
Purchase #7	$19.65	4.656%	$20.5649	$20.56	$20.55	$20.60
7 purchase totals =	$953.56		$1,019.1505	$1,019.14	$1,019.15	$1,019.20