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	$172.51	11.733%	$192.7506	$192.75	$192.75	$192.80
Purchase #2	$159.68	8.856%	$173.8213	$173.82	$173.80	$173.80
Purchase #3	$52.76	5.523%	$55.6739	$55.67	$55.65	$55.70
Purchase #4	$42.53	5.287%	$44.7786	$44.78	$44.80	$44.80
Purchase #5	$195.43	13.752%	$222.3055	$222.31	$222.30	$222.30
Purchase #6	$153.37	5.836%	$162.3207	$162.32	$162.30	$162.30
Purchase #7	$45.39	5.139%	$47.7226	$47.72	$47.70	$47.70
7 purchase totals =	$821.67		$899.3732	$899.37	$899.30	$899.40