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	$97.76	8.346%	$105.919	$105.92	$105.90	$105.90
Purchase #2	$156.66	13.774%	$178.2383	$178.24	$178.25	$178.20
Purchase #3	$17.53	8.750%	$19.0639	$19.06	$19.05	$19.10
Purchase #4	$42.38	7.732%	$45.6568	$45.66	$45.65	$45.70
Purchase #5	$127.75	13.721%	$145.2786	$145.28	$145.30	$145.30
Purchase #6	$66.85	5.526%	$70.5441	$70.54	$70.55	$70.50
Purchase #7	$123.53	4.314%	$128.8591	$128.86	$128.85	$128.90
7 purchase totals =	$632.46		$693.5598	$693.56	$693.55	$693.60