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	$158.95	4.679%	$166.3873	$166.39	$166.40	$166.40
Purchase #2	$64.75	4.289%	$67.5271	$67.53	$67.55	$67.50
Purchase #3	$182.83	4.260%	$190.6186	$190.62	$190.60	$190.60
Purchase #4	$103.30	7.672%	$111.2252	$111.23	$111.25	$111.20
Purchase #5	$145.27	6.195%	$154.2695	$154.27	$154.25	$154.30
Purchase #6	$211.74	7.476%	$227.5697	$227.57	$227.55	$227.60
Purchase #7	$27.51	10.154%	$30.3034	$30.30	$30.30	$30.30
7 purchase totals =	$894.35		$947.9008	$947.91	$947.90	$947.90