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	$132.82	7.257%	$142.4587	$142.46	$142.45	$142.50
Purchase #2	$17.96	13.328%	$20.3537	$20.35	$20.35	$20.40
Purchase #3	$33.87	9.715%	$37.1605	$37.16	$37.15	$37.20
Purchase #4	$65.72	10.739%	$72.7777	$72.78	$72.80	$72.80
Purchase #5	$247.58	6.128%	$262.7517	$262.75	$262.75	$262.80
Purchase #6	$144.74	10.173%	$159.4644	$159.46	$159.45	$159.50
Purchase #7	$183.63	11.267%	$204.3196	$204.32	$204.30	$204.30
7 purchase totals =	$826.32		$899.2863	$899.28	$899.25	$899.50