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	$56.77	5.466%	$59.873	$59.87	$59.85	$59.90
Purchase #2	$9.69	6.668%	$10.3361	$10.34	$10.35	$10.30
Purchase #3	$87.64	3.803%	$90.9729	$90.97	$90.95	$91.00
Purchase #4	$89.35	8.797%	$97.2101	$97.21	$97.20	$97.20
Purchase #5	$144.73	4.395%	$151.0909	$151.09	$151.10	$151.10
Purchase #6	$60.82	12.243%	$68.2662	$68.27	$68.25	$68.30
Purchase #7	$145.41	8.752%	$158.1363	$158.14	$158.15	$158.10
7 purchase totals =	$594.41		$635.8855	$635.89	$635.85	$635.90