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	$152.65	13.412%	$173.1234	$173.12	$173.10	$173.10
Purchase #2	$183.35	5.143%	$192.7797	$192.78	$192.80	$192.80
Purchase #3	$15.44	6.601%	$16.4592	$16.46	$16.45	$16.50
Purchase #4	$91.43	10.167%	$100.7257	$100.73	$100.75	$100.70
Purchase #5	$148.51	9.409%	$162.4833	$162.48	$162.50	$162.50
Purchase #6	$118.79	10.392%	$131.1347	$131.13	$131.15	$131.10
Purchase #7	$158.52	13.511%	$179.9376	$179.94	$179.95	$179.90
7 purchase totals =	$868.69		$956.6436	$956.64	$956.70	$956.60