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	$196.54	10.837%	$217.839	$217.84	$217.85	$217.80
Purchase #2	$117.90	12.470%	$132.6021	$132.60	$132.60	$132.60
Purchase #3	$168.30	9.258%	$183.8812	$183.88	$183.90	$183.90
Purchase #4	$94.26	10.282%	$103.9518	$103.95	$103.95	$104.00
Purchase #5	$118.60	10.707%	$131.2985	$131.30	$131.30	$131.30
Purchase #6	$6.59	4.237%	$6.8692	$6.87	$6.85	$6.90
Purchase #7	$28.31	13.267%	$32.0659	$32.07	$32.05	$32.10
7 purchase totals =	$730.50		$808.5077	$808.51	$808.50	$808.60