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	$212.36	7.211%	$227.6733	$227.67	$227.65	$227.70
Purchase #2	$134.30	12.607%	$151.2312	$151.23	$151.25	$151.20
Purchase #3	$27.84	3.497%	$28.8136	$28.81	$28.80	$28.80
Purchase #4	$100.81	10.389%	$111.2832	$111.28	$111.30	$111.30
Purchase #5	$153.46	12.484%	$172.6179	$172.62	$172.60	$172.60
Purchase #6	$133.46	10.592%	$147.5961	$147.60	$147.60	$147.60
Purchase #7	$126.94	3.418%	$131.2788	$131.28	$131.30	$131.30
7 purchase totals =	$889.17		$970.4941	$970.49	$970.50	$970.50