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	$104.74	8.145%	$113.2711	$113.27	$113.25	$113.30
Purchase #2	$37.72	10.121%	$41.5376	$41.54	$41.55	$41.50
Purchase #3	$175.25	7.605%	$188.5778	$188.58	$188.60	$188.60
Purchase #4	$93.66	10.278%	$103.2864	$103.29	$103.30	$103.30
Purchase #5	$122.30	4.167%	$127.3962	$127.40	$127.40	$127.40
Purchase #6	$43.93	7.573%	$47.2568	$47.26	$47.25	$47.30
Purchase #7	$101.29	6.801%	$108.1787	$108.18	$108.20	$108.20
7 purchase totals =	$678.89		$729.5046	$729.52	$729.55	$729.60