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	$96.76	6.426%	$102.9778	$102.98	$103.00	$103.00
Purchase #2	$6.70	13.700%	$7.6179	$7.62	$7.60	$7.60
Purchase #3	$194.38	12.800%	$219.2606	$219.26	$219.25	$219.30
Purchase #4	$122.45	4.493%	$127.9517	$127.95	$127.95	$128.00
Purchase #5	$238.86	10.122%	$263.0374	$263.04	$263.05	$263.00
Purchase #6	$212.83	11.764%	$237.8673	$237.87	$237.85	$237.90
Purchase #7	$51.92	9.138%	$56.6644	$56.66	$56.65	$56.70
7 purchase totals =	$923.90		$1,015.3771	$1,015.38	$1,015.35	$1,015.50