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	$119.50	13.134%	$135.1951	$135.20	$135.20	$135.20
Purchase #2	$63.42	4.485%	$66.2644	$66.26	$66.25	$66.30
Purchase #3	$129.93	12.194%	$145.7737	$145.77	$145.75	$145.80
Purchase #4	$87.54	3.786%	$90.8543	$90.85	$90.85	$90.90
Purchase #5	$42.55	7.678%	$45.817	$45.82	$45.80	$45.80
Purchase #6	$103.49	8.219%	$111.9958	$112.00	$112.00	$112.00
Purchase #7	$115.94	9.571%	$127.0366	$127.04	$127.05	$127.00
7 purchase totals =	$662.37		$722.9369	$722.94	$722.90	$723.00