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	$57.37	5.841%	$60.721	$60.72	$60.70	$60.70
Purchase #2	$243.56	11.479%	$271.5183	$271.52	$271.50	$271.50
Purchase #3	$231.40	4.418%	$241.6233	$241.62	$241.60	$241.60
Purchase #4	$137.98	5.805%	$145.9897	$145.99	$146.00	$146.00
Purchase #5	$9.78	10.828%	$10.839	$10.84	$10.85	$10.80
Purchase #6	$99.89	5.148%	$105.0323	$105.03	$105.05	$105.00
Purchase #7	$206.42	11.139%	$229.4131	$229.41	$229.40	$229.40
7 purchase totals =	$986.40		$1,065.1367	$1,065.13	$1,065.10	$1,065.00