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	$95.70	10.515%	$105.7629	$105.76	$105.75	$105.80
Purchase #2	$110.80	5.690%	$117.1045	$117.10	$117.10	$117.10
Purchase #3	$247.87	9.772%	$272.0919	$272.09	$272.10	$272.10
Purchase #4	$19.76	5.337%	$20.8146	$20.81	$20.80	$20.80
Purchase #5	$161.54	13.660%	$183.6064	$183.61	$183.60	$183.60
Purchase #6	$78.81	13.371%	$89.3477	$89.35	$89.35	$89.30
Purchase #7	$102.85	5.607%	$108.6168	$108.62	$108.60	$108.60
7 purchase totals =	$817.33		$897.3448	$897.34	$897.30	$897.30