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	$72.27	7.537%	$77.717	$77.72	$77.70	$77.70
Purchase #2	$99.63	11.761%	$111.3475	$111.35	$111.35	$111.30
Purchase #3	$118.73	7.343%	$127.4483	$127.45	$127.45	$127.40
Purchase #4	$116.54	9.254%	$127.3246	$127.32	$127.30	$127.30
Purchase #5	$41.66	3.634%	$43.1739	$43.17	$43.15	$43.20
Purchase #6	$44.83	10.867%	$49.7017	$49.70	$49.70	$49.70
Purchase #7	$60.87	6.149%	$64.6129	$64.61	$64.60	$64.60
7 purchase totals =	$554.53		$601.3259	$601.32	$601.25	$601.20