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	$186.83	11.492%	$208.3005	$208.30	$208.30	$208.30
Purchase #2	$221.30	4.643%	$231.575	$231.58	$231.60	$231.60
Purchase #3	$171.51	10.695%	$189.853	$189.85	$189.85	$189.90
Purchase #4	$183.73	11.315%	$204.519	$204.52	$204.50	$204.50
Purchase #5	$157.64	13.725%	$179.2761	$179.28	$179.30	$179.30
Purchase #6	$166.45	13.359%	$188.6861	$188.69	$188.70	$188.70
Purchase #7	$119.56	3.647%	$123.9204	$123.92	$123.90	$123.90
7 purchase totals =	$1,207.02		$1,326.1301	$1,326.14	$1,326.15	$1,326.20