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	$27.38	5.729%	$28.9486	$28.95	$28.95	$28.90
Purchase #2	$42.61	5.808%	$45.0848	$45.08	$45.10	$45.10
Purchase #3	$178.40	13.660%	$202.7694	$202.77	$202.75	$202.80
Purchase #4	$130.82	13.604%	$148.6168	$148.62	$148.60	$148.60
Purchase #5	$105.28	6.256%	$111.8663	$111.87	$111.85	$111.90
Purchase #6	$74.48	8.658%	$80.9285	$80.93	$80.95	$80.90
Purchase #7	$153.52	7.214%	$164.5949	$164.59	$164.60	$164.60
7 purchase totals =	$712.49		$782.8093	$782.81	$782.80	$782.80