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	$153.40	6.170%	$162.8648	$162.86	$162.85	$162.90
Purchase #2	$77.55	13.147%	$87.7455	$87.75	$87.75	$87.70
Purchase #3	$137.38	3.563%	$142.2748	$142.27	$142.25	$142.30
Purchase #4	$148.41	6.628%	$158.2466	$158.25	$158.25	$158.20
Purchase #5	$177.63	7.435%	$190.8368	$190.84	$190.85	$190.80
Purchase #6	$17.52	10.489%	$19.3577	$19.36	$19.35	$19.40
Purchase #7	$220.35	9.765%	$241.8672	$241.87	$241.85	$241.90
7 purchase totals =	$932.24		$1,003.1934	$1,003.20	$1,003.15	$1,003.20