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	$214.75	10.858%	$238.0676	$238.07	$238.05	$238.10
Purchase #2	$108.91	8.740%	$118.4287	$118.43	$118.45	$118.40
Purchase #3	$102.34	7.163%	$109.6706	$109.67	$109.65	$109.70
Purchase #4	$165.81	4.771%	$173.7208	$173.72	$173.70	$173.70
Purchase #5	$84.77	6.600%	$90.3648	$90.36	$90.35	$90.40
Purchase #6	$96.94	4.472%	$101.2752	$101.28	$101.30	$101.30
Purchase #7	$216.62	12.416%	$243.5155	$243.52	$243.50	$243.50
7 purchase totals =	$990.14		$1,075.0432	$1,075.05	$1,075.00	$1,075.10