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	$97.54	3.182%	$100.6437	$100.64	$100.65	$100.60
Purchase #2	$45.80	6.570%	$48.8091	$48.81	$48.80	$48.80
Purchase #3	$79.48	13.603%	$90.2917	$90.29	$90.30	$90.30
Purchase #4	$26.31	4.455%	$27.4821	$27.48	$27.50	$27.50
Purchase #5	$191.86	13.647%	$218.0431	$218.04	$218.05	$218.00
Purchase #6	$52.69	5.522%	$55.5995	$55.60	$55.60	$55.60
Purchase #7	$102.82	9.753%	$112.848	$112.85	$112.85	$112.80
7 purchase totals =	$596.50		$653.7172	$653.71	$653.75	$653.60