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	$130.72	10.360%	$144.2626	$144.26	$144.25	$144.30
Purchase #2	$130.96	10.480%	$144.6846	$144.68	$144.70	$144.70
Purchase #3	$70.62	10.261%	$77.8663	$77.87	$77.85	$77.90
Purchase #4	$43.43	6.380%	$46.2008	$46.20	$46.20	$46.20
Purchase #5	$176.71	5.149%	$185.8088	$185.81	$185.80	$185.80
Purchase #6	$99.76	9.305%	$109.0427	$109.04	$109.05	$109.00
Purchase #7	$114.94	13.491%	$130.4466	$130.45	$130.45	$130.40
7 purchase totals =	$767.14		$838.3124	$838.31	$838.30	$838.30