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	$146.52	3.327%	$151.3947	$151.39	$151.40	$151.40
Purchase #2	$172.72	7.423%	$185.541	$185.54	$185.55	$185.50
Purchase #3	$126.31	3.843%	$131.1641	$131.16	$131.15	$131.20
Purchase #4	$146.26	9.482%	$160.1284	$160.13	$160.15	$160.10
Purchase #5	$62.66	6.176%	$66.5299	$66.53	$66.55	$66.50
Purchase #6	$34.89	3.467%	$36.0996	$36.10	$36.10	$36.10
Purchase #7	$210.57	13.278%	$238.5295	$238.53	$238.55	$238.50
7 purchase totals =	$899.93		$969.3872	$969.38	$969.45	$969.30