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	$218.54	3.483%	$226.1517	$226.15	$226.15	$226.20
Purchase #2	$35.28	7.482%	$37.9196	$37.92	$37.90	$37.90
Purchase #3	$123.39	8.723%	$134.1533	$134.15	$134.15	$134.20
Purchase #4	$190.37	7.144%	$203.97	$203.97	$203.95	$204.00
Purchase #5	$119.25	6.852%	$127.421	$127.42	$127.40	$127.40
Purchase #6	$250.41	11.510%	$279.2322	$279.23	$279.25	$279.20
Purchase #7	$250.58	11.335%	$278.9832	$278.98	$279.00	$279.00
7 purchase totals =	$1,187.82		$1,287.8310	$1,287.82	$1,287.80	$1,287.90