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	$95.60	10.311%	$105.4573	$105.46	$105.45	$105.50
Purchase #2	$160.38	5.149%	$168.638	$168.64	$168.65	$168.60
Purchase #3	$32.73	3.125%	$33.7528	$33.75	$33.75	$33.80
Purchase #4	$98.72	12.818%	$111.3739	$111.37	$111.35	$111.40
Purchase #5	$47.73	7.667%	$51.3895	$51.39	$51.40	$51.40
Purchase #6	$101.37	11.672%	$113.2019	$113.20	$113.20	$113.20
Purchase #7	$19.35	11.150%	$21.5075	$21.51	$21.50	$21.50
7 purchase totals =	$555.88		$605.3209	$605.32	$605.30	$605.40