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	$173.55	6.623%	$185.0442	$185.04	$185.05	$185.00
Purchase #2	$217.47	7.363%	$233.4823	$233.48	$233.50	$233.50
Purchase #3	$44.88	12.131%	$50.3244	$50.32	$50.30	$50.30
Purchase #4	$19.39	9.832%	$21.2964	$21.30	$21.30	$21.30
Purchase #5	$230.58	9.247%	$251.9017	$251.90	$251.90	$251.90
Purchase #6	$12.63	7.550%	$13.5836	$13.58	$13.60	$13.60
Purchase #7	$230.88	3.161%	$238.1781	$238.18	$238.20	$238.20
7 purchase totals =	$929.38		$993.8107	$993.80	$993.85	$993.80