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	$117.49	8.497%	$127.4731	$127.47	$127.45	$127.50
Purchase #2	$167.72	8.528%	$182.0232	$182.02	$182.00	$182.00
Purchase #3	$150.64	9.681%	$165.2235	$165.22	$165.20	$165.20
Purchase #4	$232.88	8.133%	$251.8201	$251.82	$251.80	$251.80
Purchase #5	$159.58	3.514%	$165.1876	$165.19	$165.20	$165.20
Purchase #6	$187.94	9.846%	$206.4446	$206.44	$206.45	$206.40
Purchase #7	$184.60	3.157%	$190.4278	$190.43	$190.45	$190.40
7 purchase totals =	$1,200.85		$1,288.5999	$1,288.59	$1,288.55	$1,288.50