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	$59.59	3.512%	$61.6828	$61.68	$61.70	$61.70
Purchase #2	$11.97	13.261%	$13.5573	$13.56	$13.55	$13.60
Purchase #3	$26.45	13.102%	$29.9155	$29.92	$29.90	$29.90
Purchase #4	$75.91	5.622%	$80.1777	$80.18	$80.20	$80.20
Purchase #5	$39.40	8.583%	$42.7817	$42.78	$42.80	$42.80
Purchase #6	$79.45	12.124%	$89.0825	$89.08	$89.10	$89.10
Purchase #7	$199.25	10.836%	$220.8407	$220.84	$220.85	$220.80
7 purchase totals =	$492.02		$538.0382	$538.04	$538.10	$538.10