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	$100.47	5.363%	$105.8582	$105.86	$105.85	$105.90
Purchase #2	$141.94	12.358%	$159.4809	$159.48	$159.50	$159.50
Purchase #3	$229.94	9.679%	$252.1959	$252.20	$252.20	$252.20
Purchase #4	$141.27	7.256%	$151.5206	$151.52	$151.50	$151.50
Purchase #5	$234.96	5.481%	$247.8382	$247.84	$247.85	$247.80
Purchase #6	$224.53	13.570%	$254.9987	$255.00	$255.00	$255.00
Purchase #7	$41.69	8.826%	$45.3696	$45.37	$45.35	$45.40
7 purchase totals =	$1,114.80		$1,217.2621	$1,217.27	$1,217.25	$1,217.30