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	$67.83	4.469%	$70.8613	$70.86	$70.85	$70.90
Purchase #2	$19.68	10.680%	$21.7818	$21.78	$21.80	$21.80
Purchase #3	$54.41	13.428%	$61.7162	$61.72	$61.70	$61.70
Purchase #4	$93.44	11.478%	$104.165	$104.17	$104.15	$104.20
Purchase #5	$240.39	12.874%	$271.3378	$271.34	$271.35	$271.30
Purchase #6	$44.84	6.126%	$47.5869	$47.59	$47.60	$47.60
Purchase #7	$245.90	4.297%	$256.4663	$256.47	$256.45	$256.50
7 purchase totals =	$766.49		$833.9153	$833.93	$833.90	$834.00