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	$151.52	11.287%	$168.6221	$168.62	$168.60	$168.60
Purchase #2	$134.48	4.864%	$141.0211	$141.02	$141.00	$141.00
Purchase #3	$20.62	5.874%	$21.8312	$21.83	$21.85	$21.80
Purchase #4	$148.88	11.852%	$166.5253	$166.53	$166.55	$166.50
Purchase #5	$242.95	5.715%	$256.8346	$256.83	$256.85	$256.80
Purchase #6	$156.68	13.784%	$178.2768	$178.28	$178.30	$178.30
Purchase #7	$145.84	3.797%	$151.3775	$151.38	$151.40	$151.40
7 purchase totals =	$1,000.97		$1,084.4886	$1,084.49	$1,084.55	$1,084.40