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	$48.36	12.563%	$54.4355	$54.44	$54.45	$54.40
Purchase #2	$57.25	3.154%	$59.0557	$59.06	$59.05	$59.10
Purchase #3	$13.60	7.831%	$14.665	$14.67	$14.65	$14.70
Purchase #4	$66.57	5.354%	$70.1342	$70.13	$70.15	$70.10
Purchase #5	$85.76	3.163%	$88.4726	$88.47	$88.45	$88.50
Purchase #6	$65.92	10.464%	$72.8179	$72.82	$72.80	$72.80
Purchase #7	$246.58	9.695%	$270.4859	$270.49	$270.50	$270.50
7 purchase totals =	$584.04		$630.0668	$630.08	$630.05	$630.10