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	$100.81	10.716%	$111.6128	$111.61	$111.60	$111.60
Purchase #2	$33.89	8.724%	$36.8466	$36.85	$36.85	$36.80
Purchase #3	$73.85	3.578%	$76.4924	$76.49	$76.50	$76.50
Purchase #4	$226.55	10.868%	$251.1715	$251.17	$251.15	$251.20
Purchase #5	$234.38	12.253%	$263.0986	$263.10	$263.10	$263.10
Purchase #6	$73.29	12.237%	$82.2585	$82.26	$82.25	$82.30
Purchase #7	$102.26	5.701%	$108.0898	$108.09	$108.10	$108.10
7 purchase totals =	$845.03		$929.5702	$929.57	$929.55	$929.60