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	4.232%	$223.8382	$223.84	$223.85	$223.80
Purchase #2	$9.51	7.576%	$10.2305	$10.23	$10.25	$10.20
Purchase #3	$81.42	9.458%	$89.1207	$89.12	$89.10	$89.10
Purchase #4	$96.73	3.599%	$100.2113	$100.21	$100.20	$100.20
Purchase #5	$24.53	5.248%	$25.8173	$25.82	$25.80	$25.80
Purchase #6	$11.66	6.627%	$12.4327	$12.43	$12.45	$12.40
Purchase #7	$85.54	12.821%	$96.5071	$96.51	$96.50	$96.50
7 purchase totals =	$524.14		$558.1578	$558.16	$558.15	$558.00