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	$238.52	13.782%	$271.3928	$271.39	$271.40	$271.40
Purchase #2	$227.25	12.405%	$255.4404	$255.44	$255.45	$255.40
Purchase #3	$12.30	11.778%	$13.7487	$13.75	$13.75	$13.70
Purchase #4	$231.52	13.466%	$262.6965	$262.70	$262.70	$262.70
Purchase #5	$85.73	9.599%	$93.9592	$93.96	$93.95	$94.00
Purchase #6	$58.76	4.577%	$61.4494	$61.45	$61.45	$61.40
Purchase #7	$42.96	4.620%	$44.9448	$44.94	$44.95	$44.90
7 purchase totals =	$897.04		$1,003.6318	$1,003.63	$1,003.65	$1,003.50