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	$148.45	6.303%	$157.8068	$157.81	$157.80	$157.80
Purchase #2	$177.44	4.357%	$185.1711	$185.17	$185.15	$185.20
Purchase #3	$142.33	12.531%	$160.1654	$160.17	$160.15	$160.20
Purchase #4	$178.60	12.465%	$200.8625	$200.86	$200.85	$200.90
Purchase #5	$60.61	3.742%	$62.878	$62.88	$62.90	$62.90
Purchase #6	$214.57	9.291%	$234.5057	$234.51	$234.50	$234.50
Purchase #7	$56.97	8.139%	$61.6068	$61.61	$61.60	$61.60
7 purchase totals =	$978.97		$1,062.9963	$1,063.01	$1,062.95	$1,063.10