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	$133.68	13.217%	$151.3485	$151.35	$151.35	$151.30
Purchase #2	$57.39	13.525%	$65.152	$65.15	$65.15	$65.20
Purchase #3	$82.53	8.541%	$89.5789	$89.58	$89.60	$89.60
Purchase #4	$203.35	13.159%	$230.1088	$230.11	$230.10	$230.10
Purchase #5	$126.87	13.818%	$144.4009	$144.40	$144.40	$144.40
Purchase #6	$142.67	6.407%	$151.8109	$151.81	$151.80	$151.80
Purchase #7	$32.49	5.752%	$34.3588	$34.36	$34.35	$34.40
7 purchase totals =	$778.98		$866.7588	$866.76	$866.75	$866.80