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	$222.98	7.760%	$240.2832	$240.28	$240.30	$240.30
Purchase #2	$51.81	5.812%	$54.8212	$54.82	$54.80	$54.80
Purchase #3	$17.74	10.241%	$19.5568	$19.56	$19.55	$19.60
Purchase #4	$69.70	9.658%	$76.4316	$76.43	$76.45	$76.40
Purchase #5	$134.92	11.326%	$150.201	$150.20	$150.20	$150.20
Purchase #6	$106.55	5.640%	$112.5594	$112.56	$112.55	$112.60
Purchase #7	$87.76	3.263%	$90.6236	$90.62	$90.60	$90.60
7 purchase totals =	$691.46		$744.4768	$744.47	$744.45	$744.50