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	$67.81	10.513%	$74.9389	$74.94	$74.95	$74.90
Purchase #2	$158.59	12.123%	$177.8159	$177.82	$177.80	$177.80
Purchase #3	$31.82	6.395%	$33.8549	$33.85	$33.85	$33.90
Purchase #4	$211.39	11.493%	$235.6851	$235.69	$235.70	$235.70
Purchase #5	$117.25	13.310%	$132.856	$132.86	$132.85	$132.90
Purchase #6	$175.42	9.160%	$191.4885	$191.49	$191.50	$191.50
Purchase #7	$249.89	12.691%	$281.6035	$281.60	$281.60	$281.60
7 purchase totals =	$1,012.17		$1,128.2428	$1,128.25	$1,128.25	$1,128.30