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	$118.72	7.269%	$127.3498	$127.35	$127.35	$127.30
Purchase #2	$104.60	6.576%	$111.4785	$111.48	$111.50	$111.50
Purchase #3	$163.73	11.587%	$182.7014	$182.70	$182.70	$182.70
Purchase #4	$249.28	8.142%	$269.5764	$269.58	$269.60	$269.60
Purchase #5	$50.50	5.593%	$53.3245	$53.32	$53.30	$53.30
Purchase #6	$28.36	4.787%	$29.7176	$29.72	$29.70	$29.70
Purchase #7	$169.54	11.291%	$188.6828	$188.68	$188.70	$188.70
7 purchase totals =	$884.73		$962.8310	$962.83	$962.85	$962.80