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	$62.51	3.610%	$64.7666	$64.77	$64.75	$64.80
Purchase #2	$135.97	5.277%	$143.1451	$143.15	$143.15	$143.10
Purchase #3	$57.26	4.732%	$59.9695	$59.97	$59.95	$60.00
Purchase #4	$99.72	4.776%	$104.4826	$104.48	$104.50	$104.50
Purchase #5	$166.28	9.301%	$181.7457	$181.75	$181.75	$181.70
Purchase #6	$231.85	4.113%	$241.386	$241.39	$241.40	$241.40
Purchase #7	$112.72	5.658%	$119.0977	$119.10	$119.10	$119.10
7 purchase totals =	$866.31		$914.5932	$914.61	$914.60	$914.60