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	$156.45	3.505%	$161.9336	$161.93	$161.95	$161.90
Purchase #2	$28.61	13.527%	$32.4801	$32.48	$32.50	$32.50
Purchase #3	$158.90	5.396%	$167.4742	$167.47	$167.45	$167.50
Purchase #4	$134.56	12.335%	$151.158	$151.16	$151.15	$151.20
Purchase #5	$237.44	12.501%	$267.1224	$267.12	$267.10	$267.10
Purchase #6	$132.27	7.418%	$142.0818	$142.08	$142.10	$142.10
Purchase #7	$183.52	4.693%	$192.1326	$192.13	$192.15	$192.10
7 purchase totals =	$1,031.75		$1,114.3827	$1,114.37	$1,114.40	$1,114.40