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	$103.60	3.566%	$107.2944	$107.29	$107.30	$107.30
Purchase #2	$177.36	6.472%	$188.8387	$188.84	$188.85	$188.80
Purchase #3	$220.62	3.680%	$228.7388	$228.74	$228.75	$228.70
Purchase #4	$98.59	12.867%	$111.2756	$111.28	$111.30	$111.30
Purchase #5	$218.57	10.290%	$241.0609	$241.06	$241.05	$241.10
Purchase #6	$18.51	4.229%	$19.2928	$19.29	$19.30	$19.30
Purchase #7	$115.34	6.863%	$123.2558	$123.26	$123.25	$123.30
7 purchase totals =	$952.59		$1,019.7570	$1,019.76	$1,019.80	$1,019.80