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	$116.42	5.793%	$123.1642	$123.16	$123.15	$123.20
Purchase #2	$90.61	12.359%	$101.8085	$101.81	$101.80	$101.80
Purchase #3	$103.40	3.104%	$106.6095	$106.61	$106.60	$106.60
Purchase #4	$186.78	10.264%	$205.9511	$205.95	$205.95	$206.00
Purchase #5	$159.28	6.399%	$169.4723	$169.47	$169.45	$169.50
Purchase #6	$219.52	10.409%	$242.3698	$242.37	$242.35	$242.40
Purchase #7	$183.52	4.157%	$191.1489	$191.15	$191.15	$191.10
7 purchase totals =	$1,059.53		$1,140.5243	$1,140.52	$1,140.45	$1,140.60