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	$88.80	4.539%	$92.8306	$92.83	$92.85	$92.80
Purchase #2	$205.56	13.405%	$233.1153	$233.12	$233.10	$233.10
Purchase #3	$83.42	5.860%	$88.3084	$88.31	$88.30	$88.30
Purchase #4	$175.41	12.266%	$196.9258	$196.93	$196.95	$196.90
Purchase #5	$65.29	13.693%	$74.2302	$74.23	$74.25	$74.20
Purchase #6	$120.40	6.130%	$127.7805	$127.78	$127.80	$127.80
Purchase #7	$223.32	5.772%	$236.21	$236.21	$236.20	$236.20
7 purchase totals =	$962.20		$1,049.4008	$1,049.41	$1,049.45	$1,049.30