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	$36.55	4.600%	$38.2313	$38.23	$38.25	$38.20
Purchase #2	$64.62	11.745%	$72.2096	$72.21	$72.20	$72.20
Purchase #3	$106.71	11.328%	$118.7981	$118.80	$118.80	$118.80
Purchase #4	$90.56	11.527%	$100.9989	$101.00	$101.00	$101.00
Purchase #5	$166.92	3.542%	$172.8323	$172.83	$172.85	$172.80
Purchase #6	$99.38	9.168%	$108.4912	$108.49	$108.50	$108.50
Purchase #7	$100.98	6.465%	$107.5084	$107.51	$107.50	$107.50
7 purchase totals =	$665.72		$719.0698	$719.07	$719.10	$719.00