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	$205.72	5.333%	$216.691	$216.69	$216.70	$216.70
Purchase #2	$108.65	13.824%	$123.6698	$123.67	$123.65	$123.70
Purchase #3	$172.97	13.481%	$196.2881	$196.29	$196.30	$196.30
Purchase #4	$135.96	11.676%	$151.8347	$151.83	$151.85	$151.80
Purchase #5	$42.59	10.472%	$47.05	$47.05	$47.05	$47.10
Purchase #6	$122.80	12.486%	$138.1328	$138.13	$138.15	$138.10
Purchase #7	$150.34	10.182%	$165.6476	$165.65	$165.65	$165.60
7 purchase totals =	$939.03		$1,039.3140	$1,039.31	$1,039.35	$1,039.30