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	$101.42	4.428%	$105.9109	$105.91	$105.90	$105.90
Purchase #2	$19.58	7.625%	$21.073	$21.07	$21.05	$21.10
Purchase #3	$81.46	11.450%	$90.7872	$90.79	$90.80	$90.80
Purchase #4	$59.49	4.484%	$62.1575	$62.16	$62.15	$62.20
Purchase #5	$183.30	8.823%	$199.4726	$199.47	$199.45	$199.50
Purchase #6	$161.80	10.254%	$178.391	$178.39	$178.40	$178.40
Purchase #7	$101.45	4.487%	$106.0021	$106.00	$106.00	$106.00
7 purchase totals =	$708.50		$763.7943	$763.79	$763.75	$763.90