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	$179.40	5.653%	$189.5415	$189.54	$189.55	$189.50
Purchase #2	$171.89	7.324%	$184.4792	$184.48	$184.50	$184.50
Purchase #3	$228.93	4.103%	$238.323	$238.32	$238.30	$238.30
Purchase #4	$92.70	13.679%	$105.3804	$105.38	$105.40	$105.40
Purchase #5	$54.69	4.812%	$57.3217	$57.32	$57.30	$57.30
Purchase #6	$65.30	8.147%	$70.62	$70.62	$70.60	$70.60
Purchase #7	$154.38	10.121%	$170.0048	$170.00	$170.00	$170.00
7 purchase totals =	$947.29		$1,015.6706	$1,015.66	$1,015.65	$1,015.60