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	$197.88	12.712%	$223.0345	$223.03	$223.05	$223.00
Purchase #2	$104.53	6.358%	$111.176	$111.18	$111.20	$111.20
Purchase #3	$60.45	13.495%	$68.6077	$68.61	$68.60	$68.60
Purchase #4	$229.86	4.133%	$239.3601	$239.36	$239.35	$239.40
Purchase #5	$54.65	10.371%	$60.3178	$60.32	$60.30	$60.30
Purchase #6	$141.85	7.278%	$152.1738	$152.17	$152.15	$152.20
Purchase #7	$143.36	7.256%	$153.7622	$153.76	$153.75	$153.80
7 purchase totals =	$932.58		$1,008.4321	$1,008.43	$1,008.40	$1,008.50