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	$132.97	7.308%	$142.6874	$142.69	$142.70	$142.70
Purchase #2	$167.53	4.469%	$175.0169	$175.02	$175.00	$175.00
Purchase #3	$70.97	5.354%	$74.7697	$74.77	$74.75	$74.80
Purchase #4	$107.73	5.434%	$113.584	$113.58	$113.60	$113.60
Purchase #5	$116.57	6.190%	$123.7857	$123.79	$123.80	$123.80
Purchase #6	$150.52	5.301%	$158.4991	$158.50	$158.50	$158.50
Purchase #7	$112.30	13.532%	$127.4964	$127.50	$127.50	$127.50
7 purchase totals =	$858.59		$915.8392	$915.85	$915.85	$915.90