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	$175.52	5.675%	$185.4808	$185.48	$185.50	$185.50
Purchase #2	$241.67	12.613%	$272.1518	$272.15	$272.15	$272.20
Purchase #3	$158.77	11.786%	$177.4826	$177.48	$177.50	$177.50
Purchase #4	$54.84	13.614%	$62.3059	$62.31	$62.30	$62.30
Purchase #5	$111.28	6.546%	$118.5644	$118.56	$118.55	$118.60
Purchase #6	$114.97	7.368%	$123.441	$123.44	$123.45	$123.40
Purchase #7	$138.88	6.190%	$147.4767	$147.48	$147.50	$147.50
7 purchase totals =	$995.93		$1,086.9032	$1,086.90	$1,086.95	$1,087.00