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	$194.91	10.565%	$215.5022	$215.50	$215.50	$215.50
Purchase #2	$33.50	8.869%	$36.4711	$36.47	$36.45	$36.50
Purchase #3	$29.96	5.449%	$31.5925	$31.59	$31.60	$31.60
Purchase #4	$168.75	12.762%	$190.2859	$190.29	$190.30	$190.30
Purchase #5	$232.28	4.538%	$242.8209	$242.82	$242.80	$242.80
Purchase #6	$150.44	5.291%	$158.3998	$158.40	$158.40	$158.40
Purchase #7	$7.78	4.784%	$8.1522	$8.15	$8.15	$8.20
7 purchase totals =	$817.62		$883.2246	$883.22	$883.20	$883.30