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	$70.63	5.809%	$74.7329	$74.73	$74.75	$74.70
Purchase #2	$247.94	4.254%	$258.4874	$258.49	$258.50	$258.50
Purchase #3	$189.29	13.109%	$214.104	$214.10	$214.10	$214.10
Purchase #4	$89.30	12.307%	$100.2902	$100.29	$100.30	$100.30
Purchase #5	$131.95	12.467%	$148.4002	$148.40	$148.40	$148.40
Purchase #6	$202.76	13.308%	$229.7433	$229.74	$229.75	$229.70
Purchase #7	$68.34	6.568%	$72.8286	$72.83	$72.85	$72.80
7 purchase totals =	$1,000.21		$1,098.5866	$1,098.58	$1,098.65	$1,098.50