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	$141.49	5.309%	$149.0017	$149.00	$149.00	$149.00
Purchase #2	$203.78	11.645%	$227.5102	$227.51	$227.50	$227.50
Purchase #3	$70.32	11.554%	$78.4448	$78.44	$78.45	$78.40
Purchase #4	$48.86	8.501%	$53.0136	$53.01	$53.00	$53.00
Purchase #5	$137.26	13.109%	$155.2534	$155.25	$155.25	$155.30
Purchase #6	$169.42	13.513%	$192.3137	$192.31	$192.30	$192.30
Purchase #7	$144.68	8.213%	$156.5626	$156.56	$156.55	$156.60
7 purchase totals =	$915.81		$1,012.1000	$1,012.08	$1,012.05	$1,012.10