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	$77.64	6.573%	$82.7433	$82.74	$82.75	$82.70
Purchase #2	$78.45	13.773%	$89.2549	$89.25	$89.25	$89.30
Purchase #3	$48.86	4.677%	$51.1452	$51.15	$51.15	$51.10
Purchase #4	$168.90	10.409%	$186.4808	$186.48	$186.50	$186.50
Purchase #5	$220.77	6.213%	$234.4864	$234.49	$234.50	$234.50
Purchase #6	$44.47	4.667%	$46.5454	$46.55	$46.55	$46.50
Purchase #7	$116.95	5.695%	$123.6103	$123.61	$123.60	$123.60
7 purchase totals =	$756.04		$814.2663	$814.27	$814.30	$814.20