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	$44.47	9.563%	$48.7227	$48.72	$48.70	$48.70
Purchase #2	$214.73	10.652%	$237.603	$237.60	$237.60	$237.60
Purchase #3	$249.67	4.207%	$260.1736	$260.17	$260.15	$260.20
Purchase #4	$184.28	6.481%	$196.2232	$196.22	$196.20	$196.20
Purchase #5	$57.85	4.585%	$60.5024	$60.50	$60.50	$60.50
Purchase #6	$190.38	7.591%	$204.8317	$204.83	$204.85	$204.80
Purchase #7	$82.84	9.696%	$90.8722	$90.87	$90.85	$90.90
7 purchase totals =	$1,024.22		$1,098.9288	$1,098.91	$1,098.85	$1,098.90