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	$62.60	7.363%	$67.2092	$67.21	$67.20	$67.20
Purchase #2	$93.49	5.829%	$98.9395	$98.94	$98.95	$98.90
Purchase #3	$240.50	5.777%	$254.3937	$254.39	$254.40	$254.40
Purchase #4	$226.43	10.637%	$250.5154	$250.52	$250.50	$250.50
Purchase #5	$176.53	9.142%	$192.6684	$192.67	$192.65	$192.70
Purchase #6	$146.79	7.838%	$158.2954	$158.30	$158.30	$158.30
Purchase #7	$36.91	6.840%	$39.4346	$39.43	$39.45	$39.40
7 purchase totals =	$983.25		$1,061.4562	$1,061.46	$1,061.45	$1,061.40