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	$133.66	12.326%	$150.1349	$150.13	$150.15	$150.10
Purchase #2	$236.68	12.191%	$265.5337	$265.53	$265.55	$265.50
Purchase #3	$105.55	5.716%	$111.5832	$111.58	$111.60	$111.60
Purchase #4	$104.40	13.358%	$118.3458	$118.35	$118.35	$118.30
Purchase #5	$79.89	11.354%	$88.9607	$88.96	$88.95	$89.00
Purchase #6	$244.66	5.363%	$257.7811	$257.78	$257.80	$257.80
Purchase #7	$87.95	4.433%	$91.8488	$91.85	$91.85	$91.80
7 purchase totals =	$992.79		$1,084.1882	$1,084.18	$1,084.25	$1,084.10