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	$62.30	4.528%	$65.1209	$65.12	$65.10	$65.10
Purchase #2	$80.28	13.263%	$90.9275	$90.93	$90.95	$90.90
Purchase #3	$230.94	5.735%	$244.1844	$244.18	$244.20	$244.20
Purchase #4	$170.30	10.656%	$188.4472	$188.45	$188.45	$188.40
Purchase #5	$123.80	8.572%	$134.4121	$134.41	$134.40	$134.40
Purchase #6	$124.77	6.446%	$132.8127	$132.81	$132.80	$132.80
Purchase #7	$97.61	13.791%	$111.0714	$111.07	$111.05	$111.10
7 purchase totals =	$890.00		$966.9762	$966.97	$966.95	$966.90