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	$125.65	5.483%	$132.5394	$132.54	$132.55	$132.50
Purchase #2	$145.25	7.700%	$156.4343	$156.43	$156.45	$156.40
Purchase #3	$78.85	7.852%	$85.0413	$85.04	$85.05	$85.00
Purchase #4	$132.27	4.775%	$138.5859	$138.59	$138.60	$138.60
Purchase #5	$112.37	3.648%	$116.4693	$116.47	$116.45	$116.50
Purchase #6	$226.25	13.410%	$256.5901	$256.59	$256.60	$256.60
Purchase #7	$150.29	5.200%	$158.1051	$158.11	$158.10	$158.10
7 purchase totals =	$970.93		$1,043.7654	$1,043.77	$1,043.80	$1,043.70