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	$230.47	12.646%	$259.6152	$259.62	$259.60	$259.60
Purchase #2	$64.66	3.264%	$66.7705	$66.77	$66.75	$66.80
Purchase #3	$42.80	8.440%	$46.4123	$46.41	$46.40	$46.40
Purchase #4	$155.68	11.350%	$173.3497	$173.35	$173.35	$173.30
Purchase #5	$169.94	10.334%	$187.5016	$187.50	$187.50	$187.50
Purchase #6	$207.74	4.328%	$216.731	$216.73	$216.75	$216.70
Purchase #7	$45.61	13.606%	$51.8157	$51.82	$51.80	$51.80
7 purchase totals =	$916.90		$1,002.1960	$1,002.20	$1,002.15	$1,002.10