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	$153.33	3.210%	$158.2519	$158.25	$158.25	$158.30
Purchase #2	$231.54	9.476%	$253.4807	$253.48	$253.50	$253.50
Purchase #3	$188.55	5.325%	$198.5903	$198.59	$198.60	$198.60
Purchase #4	$140.40	6.838%	$150.0006	$150.00	$150.00	$150.00
Purchase #5	$172.57	6.225%	$183.3125	$183.31	$183.30	$183.30
Purchase #6	$172.61	6.673%	$184.1283	$184.13	$184.15	$184.10
Purchase #7	$10.47	9.577%	$11.4727	$11.47	$11.45	$11.50
7 purchase totals =	$1,069.47		$1,139.2370	$1,139.23	$1,139.25	$1,139.30