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	$59.75	13.153%	$67.6089	$67.61	$67.60	$67.60
Purchase #2	$117.98	12.607%	$132.8537	$132.85	$132.85	$132.90
Purchase #3	$231.27	6.259%	$245.7452	$245.75	$245.75	$245.70
Purchase #4	$33.62	12.608%	$37.8588	$37.86	$37.85	$37.90
Purchase #5	$45.43	4.648%	$47.5416	$47.54	$47.55	$47.50
Purchase #6	$46.89	5.407%	$49.4253	$49.43	$49.45	$49.40
Purchase #7	$7.53	11.609%	$8.4042	$8.40	$8.40	$8.40
7 purchase totals =	$542.47		$589.4377	$589.44	$589.45	$589.40