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	$141.71	8.568%	$153.8517	$153.85	$153.85	$153.90
Purchase #2	$40.68	4.526%	$42.5212	$42.52	$42.50	$42.50
Purchase #3	$16.59	10.223%	$18.286	$18.29	$18.30	$18.30
Purchase #4	$44.65	4.577%	$46.6936	$46.69	$46.70	$46.70
Purchase #5	$67.92	9.593%	$74.4356	$74.44	$74.45	$74.40
Purchase #6	$52.64	7.248%	$56.4553	$56.46	$56.45	$56.50
Purchase #7	$139.32	10.462%	$153.8957	$153.90	$153.90	$153.90
7 purchase totals =	$503.51		$546.1391	$546.15	$546.15	$546.20