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	$138.78	8.636%	$150.765	$150.77	$150.75	$150.80
Purchase #2	$56.96	4.554%	$59.554	$59.55	$59.55	$59.60
Purchase #3	$14.43	12.680%	$16.2597	$16.26	$16.25	$16.30
Purchase #4	$6.74	13.334%	$7.6387	$7.64	$7.65	$7.60
Purchase #5	$248.27	4.668%	$259.8592	$259.86	$259.85	$259.90
Purchase #6	$184.25	11.202%	$204.8897	$204.89	$204.90	$204.90
Purchase #7	$112.35	13.237%	$127.2218	$127.22	$127.20	$127.20
7 purchase totals =	$761.78		$826.1881	$826.19	$826.15	$826.30