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	$60.51	6.439%	$64.4062	$64.41	$64.40	$64.40
Purchase #2	$124.56	4.373%	$130.007	$130.01	$130.00	$130.00
Purchase #3	$134.61	13.830%	$153.2266	$153.23	$153.25	$153.20
Purchase #4	$78.95	3.282%	$81.5411	$81.54	$81.55	$81.50
Purchase #5	$127.77	3.182%	$131.8356	$131.84	$131.85	$131.80
Purchase #6	$169.58	8.588%	$184.1435	$184.14	$184.15	$184.10
Purchase #7	$195.52	11.320%	$217.6529	$217.65	$217.65	$217.70
7 purchase totals =	$891.50		$962.8129	$962.82	$962.85	$962.70