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	$62.48	6.837%	$66.7518	$66.75	$66.75	$66.80
Purchase #2	$72.69	7.797%	$78.3576	$78.36	$78.35	$78.40
Purchase #3	$215.47	7.376%	$231.3631	$231.36	$231.35	$231.40
Purchase #4	$197.87	7.551%	$212.8112	$212.81	$212.80	$212.80
Purchase #5	$92.30	7.724%	$99.4293	$99.43	$99.45	$99.40
Purchase #6	$48.79	12.598%	$54.9366	$54.94	$54.95	$54.90
Purchase #7	$51.96	11.327%	$57.8455	$57.85	$57.85	$57.80
7 purchase totals =	$741.56		$801.4951	$801.50	$801.50	$801.50