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	$37.39	10.361%	$41.264	$41.26	$41.25	$41.30
Purchase #2	$196.38	13.268%	$222.4357	$222.44	$222.45	$222.40
Purchase #3	$47.63	10.657%	$52.7059	$52.71	$52.70	$52.70
Purchase #4	$117.25	3.109%	$120.8953	$120.90	$120.90	$120.90
Purchase #5	$52.86	6.485%	$56.288	$56.29	$56.30	$56.30
Purchase #6	$53.28	5.502%	$56.2115	$56.21	$56.20	$56.20
Purchase #7	$18.85	9.152%	$20.5752	$20.58	$20.60	$20.60
7 purchase totals =	$523.64		$570.3756	$570.39	$570.40	$570.40