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	$100.85	13.163%	$114.1249	$114.12	$114.10	$114.10
Purchase #2	$230.97	10.873%	$256.0834	$256.08	$256.10	$256.10
Purchase #3	$91.84	3.483%	$95.0388	$95.04	$95.05	$95.00
Purchase #4	$216.79	11.716%	$242.1891	$242.19	$242.20	$242.20
Purchase #5	$231.41	8.147%	$250.263	$250.26	$250.25	$250.30
Purchase #6	$141.72	4.788%	$148.5056	$148.51	$148.50	$148.50
Purchase #7	$111.91	13.640%	$127.1745	$127.17	$127.15	$127.20
7 purchase totals =	$1,125.49		$1,233.3793	$1,233.37	$1,233.35	$1,233.40