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	$143.97	8.292%	$155.908	$155.91	$155.90	$155.90
Purchase #2	$94.94	3.463%	$98.2278	$98.23	$98.25	$98.20
Purchase #3	$108.87	13.376%	$123.4325	$123.43	$123.45	$123.40
Purchase #4	$168.96	7.460%	$181.5644	$181.56	$181.55	$181.60
Purchase #5	$117.58	10.325%	$129.7201	$129.72	$129.70	$129.70
Purchase #6	$228.45	11.427%	$254.555	$254.56	$254.55	$254.60
Purchase #7	$117.68	8.564%	$127.7581	$127.76	$127.75	$127.80
7 purchase totals =	$980.45		$1,071.1659	$1,071.17	$1,071.15	$1,071.20