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	$149.32	4.732%	$156.3858	$156.39	$156.40	$156.40
Purchase #2	$60.71	9.374%	$66.401	$66.40	$66.40	$66.40
Purchase #3	$125.77	5.866%	$133.1477	$133.15	$133.15	$133.10
Purchase #4	$18.43	12.322%	$20.7009	$20.70	$20.70	$20.70
Purchase #5	$138.56	3.273%	$143.0951	$143.10	$143.10	$143.10
Purchase #6	$102.92	6.198%	$109.299	$109.30	$109.30	$109.30
Purchase #7	$229.32	11.316%	$255.2699	$255.27	$255.25	$255.30
7 purchase totals =	$825.03		$884.2994	$884.31	$884.30	$884.30