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	$50.77	6.658%	$54.1503	$54.15	$54.15	$54.20
Purchase #2	$193.94	3.269%	$200.2799	$200.28	$200.30	$200.30
Purchase #3	$10.30	8.280%	$11.1528	$11.15	$11.15	$11.20
Purchase #4	$140.64	5.591%	$148.5032	$148.50	$148.50	$148.50
Purchase #5	$166.69	8.409%	$180.707	$180.71	$180.70	$180.70
Purchase #6	$87.75	11.847%	$98.1457	$98.15	$98.15	$98.10
Purchase #7	$104.40	6.785%	$111.4835	$111.48	$111.50	$111.50
7 purchase totals =	$754.49		$804.4224	$804.42	$804.45	$804.50