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	$204.87	9.114%	$223.5419	$223.54	$223.55	$223.50
Purchase #2	$241.29	7.587%	$259.5967	$259.60	$259.60	$259.60
Purchase #3	$123.73	4.476%	$129.2682	$129.27	$129.25	$129.30
Purchase #4	$54.52	12.545%	$61.3595	$61.36	$61.35	$61.40
Purchase #5	$99.57	12.431%	$111.9475	$111.95	$111.95	$111.90
Purchase #6	$238.44	8.596%	$258.9363	$258.94	$258.95	$258.90
Purchase #7	$208.83	11.185%	$232.1876	$232.19	$232.20	$232.20
7 purchase totals =	$1,171.25		$1,276.8377	$1,276.85	$1,276.85	$1,276.80