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	$149.77	5.516%	$158.0313	$158.03	$158.05	$158.00
Purchase #2	$138.94	8.278%	$150.4415	$150.44	$150.45	$150.40
Purchase #3	$170.30	5.396%	$179.4894	$179.49	$179.50	$179.50
Purchase #4	$156.54	10.711%	$173.307	$173.31	$173.30	$173.30
Purchase #5	$9.28	13.167%	$10.5019	$10.50	$10.50	$10.50
Purchase #6	$151.41	8.654%	$164.513	$164.51	$164.50	$164.50
Purchase #7	$128.97	10.808%	$142.9091	$142.91	$142.90	$142.90
7 purchase totals =	$905.21		$979.1932	$979.19	$979.20	$979.10