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	$70.37	6.347%	$74.8364	$74.84	$74.85	$74.80
Purchase #2	$31.28	3.636%	$32.4173	$32.42	$32.40	$32.40
Purchase #3	$125.71	13.586%	$142.789	$142.79	$142.80	$142.80
Purchase #4	$111.43	6.379%	$118.5381	$118.54	$118.55	$118.50
Purchase #5	$233.77	11.328%	$260.2515	$260.25	$260.25	$260.30
Purchase #6	$6.64	13.635%	$7.5454	$7.55	$7.55	$7.50
Purchase #7	$144.38	4.638%	$151.0763	$151.08	$151.10	$151.10
7 purchase totals =	$723.58		$787.4540	$787.47	$787.50	$787.40