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	$164.32	6.325%	$174.7132	$174.71	$174.70	$174.70
Purchase #2	$38.97	4.761%	$40.8254	$40.83	$40.85	$40.80
Purchase #3	$32.78	5.870%	$34.7042	$34.70	$34.70	$34.70
Purchase #4	$9.75	10.788%	$10.8018	$10.80	$10.80	$10.80
Purchase #5	$39.81	7.839%	$42.9307	$42.93	$42.95	$42.90
Purchase #6	$43.76	3.259%	$45.1861	$45.19	$45.20	$45.20
Purchase #7	$224.41	13.406%	$254.4944	$254.49	$254.50	$254.50
7 purchase totals =	$553.80		$603.6558	$603.65	$603.70	$603.60