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	$249.61	5.641%	$263.6905	$263.69	$263.70	$263.70
Purchase #2	$163.57	8.244%	$177.0547	$177.05	$177.05	$177.10
Purchase #3	$104.74	6.247%	$111.2831	$111.28	$111.30	$111.30
Purchase #4	$64.80	4.672%	$67.8275	$67.83	$67.85	$67.80
Purchase #5	$93.38	10.604%	$103.282	$103.28	$103.30	$103.30
Purchase #6	$139.68	9.344%	$152.7317	$152.73	$152.75	$152.70
Purchase #7	$58.85	13.272%	$66.6606	$66.66	$66.65	$66.70
7 purchase totals =	$874.63		$942.5301	$942.52	$942.60	$942.60