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	$189.39	3.710%	$196.4164	$196.42	$196.40	$196.40
Purchase #2	$20.51	10.154%	$22.5926	$22.59	$22.60	$22.60
Purchase #3	$32.47	6.814%	$34.6825	$34.68	$34.70	$34.70
Purchase #4	$108.83	13.411%	$123.4252	$123.43	$123.45	$123.40
Purchase #5	$31.88	4.351%	$33.2671	$33.27	$33.25	$33.30
Purchase #6	$6.66	12.280%	$7.4778	$7.48	$7.50	$7.50
Purchase #7	$157.65	10.346%	$173.9605	$173.96	$173.95	$174.00
7 purchase totals =	$547.39		$591.8221	$591.83	$591.85	$591.90