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	$148.62	4.577%	$155.4223	$155.42	$155.40	$155.40
Purchase #2	$238.53	3.609%	$247.1385	$247.14	$247.15	$247.10
Purchase #3	$23.46	6.763%	$25.0466	$25.05	$25.05	$25.00
Purchase #4	$17.47	7.767%	$18.8269	$18.83	$18.85	$18.80
Purchase #5	$99.69	4.636%	$104.3116	$104.31	$104.30	$104.30
Purchase #6	$174.82	9.499%	$191.4262	$191.43	$191.45	$191.40
Purchase #7	$108.72	5.445%	$114.6398	$114.64	$114.65	$114.60
7 purchase totals =	$811.31		$856.8119	$856.82	$856.85	$856.60