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	$67.68	10.326%	$74.6686	$74.67	$74.65	$74.70
Purchase #2	$119.68	6.567%	$127.5394	$127.54	$127.55	$127.50
Purchase #3	$29.88	7.345%	$32.0747	$32.07	$32.05	$32.10
Purchase #4	$55.30	11.660%	$61.748	$61.75	$61.75	$61.70
Purchase #5	$217.94	12.528%	$245.2435	$245.24	$245.25	$245.20
Purchase #6	$201.82	10.264%	$222.5348	$222.53	$222.55	$222.50
Purchase #7	$38.31	13.537%	$43.496	$43.50	$43.50	$43.50
7 purchase totals =	$730.61		$807.3050	$807.30	$807.30	$807.20