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	$155.86	12.837%	$175.8677	$175.87	$175.85	$175.90
Purchase #2	$228.77	5.755%	$241.9357	$241.94	$241.95	$241.90
Purchase #3	$157.48	9.704%	$172.7619	$172.76	$172.75	$172.80
Purchase #4	$188.44	6.195%	$200.1139	$200.11	$200.10	$200.10
Purchase #5	$182.50	5.621%	$192.7583	$192.76	$192.75	$192.80
Purchase #6	$90.94	6.422%	$96.7802	$96.78	$96.80	$96.80
Purchase #7	$6.88	10.422%	$7.597	$7.60	$7.60	$7.60
7 purchase totals =	$1,010.87		$1,087.8147	$1,087.82	$1,087.80	$1,087.90