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	$103.69	4.297%	$108.1456	$108.15	$108.15	$108.10
Purchase #2	$94.28	6.683%	$100.5807	$100.58	$100.60	$100.60
Purchase #3	$73.28	12.354%	$82.333	$82.33	$82.35	$82.30
Purchase #4	$97.88	7.327%	$105.0517	$105.05	$105.05	$105.10
Purchase #5	$151.37	11.433%	$168.6761	$168.68	$168.70	$168.70
Purchase #6	$211.58	10.664%	$234.1429	$234.14	$234.15	$234.10
Purchase #7	$129.74	6.448%	$138.1056	$138.11	$138.10	$138.10
7 purchase totals =	$861.82		$937.0356	$937.04	$937.10	$937.00