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	$167.29	12.510%	$188.218	$188.22	$188.20	$188.20
Purchase #2	$59.36	3.141%	$61.2245	$61.22	$61.20	$61.20
Purchase #3	$14.78	11.241%	$16.4414	$16.44	$16.45	$16.40
Purchase #4	$181.78	4.695%	$190.3146	$190.31	$190.30	$190.30
Purchase #5	$44.52	5.320%	$46.8885	$46.89	$46.90	$46.90
Purchase #6	$149.54	6.133%	$158.7113	$158.71	$158.70	$158.70
Purchase #7	$98.80	13.702%	$112.3376	$112.34	$112.35	$112.30
7 purchase totals =	$716.07		$774.1359	$774.13	$774.10	$774.00