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	$244.69	4.614%	$255.98	$255.98	$256.00	$256.00
Purchase #2	$155.50	11.429%	$173.2721	$173.27	$173.25	$173.30
Purchase #3	$243.31	7.635%	$261.8867	$261.89	$261.90	$261.90
Purchase #4	$216.93	11.218%	$241.2652	$241.27	$241.25	$241.30
Purchase #5	$91.66	5.724%	$96.9066	$96.91	$96.90	$96.90
Purchase #6	$242.86	12.379%	$272.9236	$272.92	$272.90	$272.90
Purchase #7	$139.59	6.146%	$148.1692	$148.17	$148.15	$148.20
7 purchase totals =	$1,334.54		$1,450.4034	$1,450.41	$1,450.35	$1,450.50