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	$96.70	13.553%	$109.8058	$109.81	$109.80	$109.80
Purchase #2	$165.29	11.346%	$184.0438	$184.04	$184.05	$184.00
Purchase #3	$116.43	9.504%	$127.4955	$127.50	$127.50	$127.50
Purchase #4	$161.90	6.575%	$172.5449	$172.54	$172.55	$172.50
Purchase #5	$221.68	10.821%	$245.668	$245.67	$245.65	$245.70
Purchase #6	$44.46	9.256%	$48.5752	$48.58	$48.60	$48.60
Purchase #7	$119.52	7.704%	$128.7278	$128.73	$128.75	$128.70
7 purchase totals =	$925.98		$1,016.8610	$1,016.87	$1,016.90	$1,016.80