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	$177.25	4.482%	$185.1943	$185.19	$185.20	$185.20
Purchase #2	$125.32	7.260%	$134.4182	$134.42	$134.40	$134.40
Purchase #3	$177.95	7.601%	$191.476	$191.48	$191.50	$191.50
Purchase #4	$118.31	12.558%	$133.1674	$133.17	$133.15	$133.20
Purchase #5	$132.90	8.256%	$143.8722	$143.87	$143.85	$143.90
Purchase #6	$46.57	13.436%	$52.8271	$52.83	$52.85	$52.80
Purchase #7	$230.44	10.461%	$254.5463	$254.55	$254.55	$254.50
7 purchase totals =	$1,008.74		$1,095.5015	$1,095.51	$1,095.50	$1,095.50