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	$52.44	3.534%	$54.2932	$54.29	$54.30	$54.30
Purchase #2	$118.80	11.119%	$132.0094	$132.01	$132.00	$132.00
Purchase #3	$173.44	7.228%	$185.9762	$185.98	$186.00	$186.00
Purchase #4	$26.66	12.339%	$29.9496	$29.95	$29.95	$29.90
Purchase #5	$96.85	4.225%	$100.9419	$100.94	$100.95	$100.90
Purchase #6	$49.29	3.264%	$50.8988	$50.90	$50.90	$50.90
Purchase #7	$166.42	10.485%	$183.8691	$183.87	$183.85	$183.90
7 purchase totals =	$683.90		$737.9382	$737.94	$737.95	$737.90