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	$22.43	8.267%	$24.2843	$24.28	$24.30	$24.30
Purchase #2	$166.84	3.395%	$172.5042	$172.50	$172.50	$172.50
Purchase #3	$163.98	11.140%	$182.2474	$182.25	$182.25	$182.20
Purchase #4	$26.42	4.298%	$27.5555	$27.56	$27.55	$27.60
Purchase #5	$62.28	6.715%	$66.4621	$66.46	$66.45	$66.50
Purchase #6	$129.90	11.261%	$144.528	$144.53	$144.55	$144.50
Purchase #7	$134.42	7.386%	$144.3483	$144.35	$144.35	$144.30
7 purchase totals =	$706.27		$761.9298	$761.93	$761.95	$761.90