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	$180.39	5.505%	$190.3205	$190.32	$190.30	$190.30
Purchase #2	$10.47	6.521%	$11.1527	$11.15	$11.15	$11.20
Purchase #3	$93.82	4.750%	$98.2765	$98.28	$98.30	$98.30
Purchase #4	$77.48	10.383%	$85.5247	$85.52	$85.50	$85.50
Purchase #5	$138.31	12.157%	$155.1243	$155.12	$155.10	$155.10
Purchase #6	$108.81	3.316%	$112.4181	$112.42	$112.40	$112.40
Purchase #7	$132.30	5.395%	$139.4376	$139.44	$139.45	$139.40
7 purchase totals =	$741.58		$792.2544	$792.25	$792.20	$792.20