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	$53.54	13.759%	$60.9066	$60.91	$60.90	$60.90
Purchase #2	$37.86	3.494%	$39.1828	$39.18	$39.20	$39.20
Purchase #3	$58.45	6.219%	$62.085	$62.09	$62.10	$62.10
Purchase #4	$96.56	8.449%	$104.7184	$104.72	$104.70	$104.70
Purchase #5	$30.91	9.262%	$33.7729	$33.77	$33.75	$33.80
Purchase #6	$217.66	7.257%	$233.4556	$233.46	$233.45	$233.50
Purchase #7	$64.25	12.491%	$72.2755	$72.28	$72.30	$72.30
7 purchase totals =	$559.23		$606.3968	$606.41	$606.40	$606.50