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	$247.73	11.622%	$276.5212	$276.52	$276.50	$276.50
Purchase #2	$14.77	5.258%	$15.5466	$15.55	$15.55	$15.50
Purchase #3	$42.83	11.376%	$47.7023	$47.70	$47.70	$47.70
Purchase #4	$136.73	11.334%	$152.227	$152.23	$152.25	$152.20
Purchase #5	$137.95	11.817%	$154.2516	$154.25	$154.25	$154.30
Purchase #6	$114.58	11.166%	$127.374	$127.37	$127.35	$127.40
Purchase #7	$133.49	4.628%	$139.6679	$139.67	$139.65	$139.70
7 purchase totals =	$828.08		$913.2906	$913.29	$913.25	$913.30