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	$197.37	5.687%	$208.5944	$208.59	$208.60	$208.60
Purchase #2	$153.43	12.625%	$172.8005	$172.80	$172.80	$172.80
Purchase #3	$174.93	12.115%	$196.1228	$196.12	$196.10	$196.10
Purchase #4	$224.35	7.649%	$241.5105	$241.51	$241.50	$241.50
Purchase #5	$98.85	10.707%	$109.4339	$109.43	$109.45	$109.40
Purchase #6	$90.54	13.474%	$102.7394	$102.74	$102.75	$102.70
Purchase #7	$47.29	8.700%	$51.4042	$51.40	$51.40	$51.40
7 purchase totals =	$986.76		$1,082.6057	$1,082.59	$1,082.60	$1,082.50