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	$142.43	4.813%	$149.2852	$149.29	$149.30	$149.30
Purchase #2	$148.54	4.779%	$155.6387	$155.64	$155.65	$155.60
Purchase #3	$232.72	13.109%	$263.2273	$263.23	$263.25	$263.20
Purchase #4	$99.46	6.356%	$105.7817	$105.78	$105.80	$105.80
Purchase #5	$107.47	6.128%	$114.0558	$114.06	$114.05	$114.10
Purchase #6	$39.52	9.106%	$43.1187	$43.12	$43.10	$43.10
Purchase #7	$102.76	13.328%	$116.4559	$116.46	$116.45	$116.50
7 purchase totals =	$872.90		$947.5633	$947.58	$947.60	$947.60