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	$198.86	11.443%	$221.6155	$221.62	$221.60	$221.60
Purchase #2	$151.89	6.278%	$161.4257	$161.43	$161.45	$161.40
Purchase #3	$164.93	11.123%	$183.2752	$183.28	$183.30	$183.30
Purchase #4	$248.84	11.755%	$278.0911	$278.09	$278.10	$278.10
Purchase #5	$55.42	5.521%	$58.4797	$58.48	$58.50	$58.50
Purchase #6	$104.38	7.197%	$111.8922	$111.89	$111.90	$111.90
Purchase #7	$176.89	12.160%	$198.3998	$198.40	$198.40	$198.40
7 purchase totals =	$1,101.21		$1,213.1792	$1,213.19	$1,213.25	$1,213.20