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	$57.99	13.706%	$65.9381	$65.94	$65.95	$65.90
Purchase #2	$39.39	5.547%	$41.575	$41.58	$41.60	$41.60
Purchase #3	$65.60	7.650%	$70.6184	$70.62	$70.60	$70.60
Purchase #4	$119.93	6.227%	$127.398	$127.40	$127.40	$127.40
Purchase #5	$116.49	5.217%	$122.5673	$122.57	$122.55	$122.60
Purchase #6	$57.72	3.583%	$59.7881	$59.79	$59.80	$59.80
Purchase #7	$225.32	6.763%	$240.5584	$240.56	$240.55	$240.60
7 purchase totals =	$682.44		$728.4433	$728.46	$728.45	$728.50