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	$105.91	5.247%	$111.4671	$111.47	$111.45	$111.50
Purchase #2	$64.59	4.394%	$67.4281	$67.43	$67.45	$67.40
Purchase #3	$209.76	3.457%	$217.0114	$217.01	$217.00	$217.00
Purchase #4	$113.53	13.610%	$128.9814	$128.98	$129.00	$129.00
Purchase #5	$66.69	8.213%	$72.1672	$72.17	$72.15	$72.20
Purchase #6	$79.74	13.844%	$90.7792	$90.78	$90.80	$90.80
Purchase #7	$80.26	9.142%	$87.5974	$87.60	$87.60	$87.60
7 purchase totals =	$720.48		$775.4318	$775.44	$775.45	$775.50