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	$61.41	7.522%	$66.0293	$66.03	$66.05	$66.00
Purchase #2	$42.83	8.367%	$46.4136	$46.41	$46.40	$46.40
Purchase #3	$94.57	11.155%	$105.1193	$105.12	$105.10	$105.10
Purchase #4	$22.91	13.165%	$25.9261	$25.93	$25.95	$25.90
Purchase #5	$190.40	7.358%	$204.4096	$204.41	$204.40	$204.40
Purchase #6	$99.75	11.792%	$111.5125	$111.51	$111.50	$111.50
Purchase #7	$234.25	6.146%	$248.647	$248.65	$248.65	$248.60
7 purchase totals =	$746.12		$808.0574	$808.06	$808.05	$807.90