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	$70.28	3.669%	$72.8586	$72.86	$72.85	$72.90
Purchase #2	$51.34	10.636%	$56.8005	$56.80	$56.80	$56.80
Purchase #3	$158.59	3.673%	$164.415	$164.42	$164.40	$164.40
Purchase #4	$77.52	12.476%	$87.1914	$87.19	$87.20	$87.20
Purchase #5	$162.72	8.224%	$176.1021	$176.10	$176.10	$176.10
Purchase #6	$66.94	8.252%	$72.4639	$72.46	$72.45	$72.50
Purchase #7	$182.57	7.131%	$195.5891	$195.59	$195.60	$195.60
7 purchase totals =	$769.96		$825.4206	$825.42	$825.40	$825.50