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	$162.50	6.136%	$172.471	$172.47	$172.45	$172.50
Purchase #2	$190.74	3.398%	$197.2213	$197.22	$197.20	$197.20
Purchase #3	$59.73	3.660%	$61.9161	$61.92	$61.90	$61.90
Purchase #4	$200.44	11.183%	$222.8552	$222.86	$222.85	$222.90
Purchase #5	$49.95	5.636%	$52.7652	$52.77	$52.75	$52.80
Purchase #6	$125.88	5.444%	$132.7329	$132.73	$132.75	$132.70
Purchase #7	$116.58	13.588%	$132.4209	$132.42	$132.40	$132.40
7 purchase totals =	$905.82		$972.3826	$972.39	$972.30	$972.40