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	$84.49	13.707%	$96.071	$96.07	$96.05	$96.10
Purchase #2	$111.62	13.815%	$127.0403	$127.04	$127.05	$127.00
Purchase #3	$23.25	13.456%	$26.3785	$26.38	$26.40	$26.40
Purchase #4	$42.64	6.257%	$45.308	$45.31	$45.30	$45.30
Purchase #5	$129.63	7.279%	$139.0658	$139.07	$139.05	$139.10
Purchase #6	$22.40	9.203%	$24.4615	$24.46	$24.45	$24.50
Purchase #7	$112.89	6.203%	$119.8926	$119.89	$119.90	$119.90
7 purchase totals =	$526.92		$578.2177	$578.22	$578.20	$578.30