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	$193.78	6.396%	$206.1742	$206.17	$206.15	$206.20
Purchase #2	$230.75	3.243%	$238.2332	$238.23	$238.25	$238.20
Purchase #3	$31.51	12.255%	$35.3716	$35.37	$35.35	$35.40
Purchase #4	$162.35	13.443%	$184.1747	$184.17	$184.15	$184.20
Purchase #5	$99.88	13.156%	$113.0202	$113.02	$113.00	$113.00
Purchase #6	$146.72	13.158%	$166.0254	$166.03	$166.05	$166.00
Purchase #7	$248.44	3.780%	$257.831	$257.83	$257.85	$257.80
7 purchase totals =	$1,113.43		$1,200.8303	$1,200.82	$1,200.80	$1,200.80