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	$88.65	9.862%	$97.3927	$97.39	$97.40	$97.40
Purchase #2	$34.84	7.197%	$37.3474	$37.35	$37.35	$37.30
Purchase #3	$76.96	5.331%	$81.0627	$81.06	$81.05	$81.10
Purchase #4	$95.76	5.337%	$100.8707	$100.87	$100.85	$100.90
Purchase #5	$245.72	13.783%	$279.5876	$279.59	$279.60	$279.60
Purchase #6	$88.61	6.239%	$94.1384	$94.14	$94.15	$94.10
Purchase #7	$9.64	5.246%	$10.1457	$10.15	$10.15	$10.10
7 purchase totals =	$640.18		$700.5452	$700.55	$700.55	$700.50