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	$42.40	7.215%	$45.4592	$45.46	$45.45	$45.50
Purchase #2	$139.71	9.797%	$153.3974	$153.40	$153.40	$153.40
Purchase #3	$88.32	10.553%	$97.6404	$97.64	$97.65	$97.60
Purchase #4	$65.84	6.688%	$70.2434	$70.24	$70.25	$70.20
Purchase #5	$58.59	3.206%	$60.4684	$60.47	$60.45	$60.50
Purchase #6	$18.80	13.155%	$21.2731	$21.27	$21.25	$21.30
Purchase #7	$47.81	4.374%	$49.9012	$49.90	$49.90	$49.90
7 purchase totals =	$461.47		$498.3831	$498.38	$498.35	$498.40