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	$152.99	6.103%	$162.327	$162.33	$162.35	$162.30
Purchase #2	$92.65	7.523%	$99.6201	$99.62	$99.60	$99.60
Purchase #3	$118.89	13.423%	$134.8486	$134.85	$134.85	$134.80
Purchase #4	$143.43	5.598%	$151.4592	$151.46	$151.45	$151.50
Purchase #5	$208.95	11.636%	$233.2634	$233.26	$233.25	$233.30
Purchase #6	$22.73	5.278%	$23.9297	$23.93	$23.95	$23.90
Purchase #7	$45.30	9.298%	$49.512	$49.51	$49.50	$49.50
7 purchase totals =	$784.94		$854.9600	$854.96	$854.95	$854.90