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	$223.41	8.582%	$242.583	$242.58	$242.60	$242.60
Purchase #2	$32.27	12.702%	$36.3689	$36.37	$36.35	$36.40
Purchase #3	$81.64	10.143%	$89.9207	$89.92	$89.90	$89.90
Purchase #4	$95.98	4.700%	$100.4911	$100.49	$100.50	$100.50
Purchase #5	$99.75	11.505%	$111.2262	$111.23	$111.25	$111.20
Purchase #6	$7.76	12.643%	$8.7411	$8.74	$8.75	$8.70
Purchase #7	$154.33	12.303%	$173.3172	$173.32	$173.30	$173.30
7 purchase totals =	$695.14		$762.6482	$762.65	$762.65	$762.60