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	$65.37	3.291%	$67.5213	$67.52	$67.50	$67.50
Purchase #2	$98.74	10.273%	$108.8836	$108.88	$108.90	$108.90
Purchase #3	$143.31	7.104%	$153.4907	$153.49	$153.50	$153.50
Purchase #4	$160.41	4.408%	$167.4809	$167.48	$167.50	$167.50
Purchase #5	$118.35	3.782%	$122.826	$122.83	$122.85	$122.80
Purchase #6	$167.49	3.409%	$173.1997	$173.20	$173.20	$173.20
Purchase #7	$246.66	6.645%	$263.0506	$263.05	$263.05	$263.10
7 purchase totals =	$1,000.33		$1,056.4528	$1,056.45	$1,056.50	$1,056.50