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	$111.83	11.642%	$124.8492	$124.85	$124.85	$124.80
Purchase #2	$56.94	4.600%	$59.5592	$59.56	$59.55	$59.60
Purchase #3	$127.63	7.528%	$137.238	$137.24	$137.25	$137.20
Purchase #4	$109.78	7.301%	$117.795	$117.80	$117.80	$117.80
Purchase #5	$221.69	10.381%	$244.7036	$244.70	$244.70	$244.70
Purchase #6	$38.83	13.503%	$44.0732	$44.07	$44.05	$44.10
Purchase #7	$96.88	8.475%	$105.0906	$105.09	$105.10	$105.10
7 purchase totals =	$763.58		$833.3088	$833.31	$833.30	$833.30