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	$125.54	5.498%	$132.4422	$132.44	$132.45	$132.40
Purchase #2	$225.47	13.581%	$256.0911	$256.09	$256.10	$256.10
Purchase #3	$11.33	8.275%	$12.2676	$12.27	$12.25	$12.30
Purchase #4	$21.61	11.157%	$24.021	$24.02	$24.00	$24.00
Purchase #5	$82.96	7.580%	$89.2484	$89.25	$89.25	$89.20
Purchase #6	$56.52	10.720%	$62.5789	$62.58	$62.60	$62.60
Purchase #7	$178.66	5.516%	$188.5149	$188.51	$188.50	$188.50
7 purchase totals =	$702.09		$765.1641	$765.16	$765.15	$765.10