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	$113.45	4.131%	$118.1366	$118.14	$118.15	$118.10
Purchase #2	$179.72	4.471%	$187.7553	$187.76	$187.75	$187.80
Purchase #3	$67.49	9.564%	$73.9447	$73.94	$73.95	$73.90
Purchase #4	$155.32	4.672%	$162.5766	$162.58	$162.60	$162.60
Purchase #5	$241.52	7.291%	$259.1292	$259.13	$259.15	$259.10
Purchase #6	$230.60	4.540%	$241.0692	$241.07	$241.05	$241.10
Purchase #7	$95.42	6.173%	$101.3103	$101.31	$101.30	$101.30
7 purchase totals =	$1,083.52		$1,143.9219	$1,143.93	$1,143.95	$1,143.90