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	$244.57	6.437%	$260.313	$260.31	$260.30	$260.30
Purchase #2	$214.93	12.316%	$241.4008	$241.40	$241.40	$241.40
Purchase #3	$18.81	3.464%	$19.4616	$19.46	$19.45	$19.50
Purchase #4	$203.74	7.374%	$218.7638	$218.76	$218.75	$218.80
Purchase #5	$173.32	13.569%	$196.8378	$196.84	$196.85	$196.80
Purchase #6	$71.39	10.104%	$78.6032	$78.60	$78.60	$78.60
Purchase #7	$115.38	12.386%	$129.671	$129.67	$129.65	$129.70
7 purchase totals =	$1,042.14		$1,145.0512	$1,145.04	$1,145.00	$1,145.10