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	$197.29	6.485%	$210.0843	$210.08	$210.10	$210.10
Purchase #2	$105.41	5.834%	$111.5596	$111.56	$111.55	$111.60
Purchase #3	$113.43	11.220%	$126.1568	$126.16	$126.15	$126.20
Purchase #4	$100.31	10.166%	$110.5075	$110.51	$110.50	$110.50
Purchase #5	$242.34	13.481%	$275.0099	$275.01	$275.00	$275.00
Purchase #6	$125.82	8.283%	$136.2417	$136.24	$136.25	$136.20
Purchase #7	$122.80	3.466%	$127.0562	$127.06	$127.05	$127.10
7 purchase totals =	$1,007.40		$1,096.6160	$1,096.62	$1,096.60	$1,096.70