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	$196.39	6.507%	$209.1691	$209.17	$209.15	$209.20
Purchase #2	$214.58	7.226%	$230.0856	$230.09	$230.10	$230.10
Purchase #3	$85.61	13.813%	$97.4353	$97.44	$97.45	$97.40
Purchase #4	$53.82	11.237%	$59.8678	$59.87	$59.85	$59.90
Purchase #5	$113.92	11.628%	$127.1666	$127.17	$127.15	$127.20
Purchase #6	$74.94	9.527%	$82.0795	$82.08	$82.10	$82.10
Purchase #7	$35.96	6.790%	$38.4017	$38.40	$38.40	$38.40
7 purchase totals =	$775.22		$844.2056	$844.22	$844.20	$844.30