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	$149.41	6.704%	$159.4264	$159.43	$159.45	$159.40
Purchase #2	$136.25	7.223%	$146.0913	$146.09	$146.10	$146.10
Purchase #3	$35.56	8.610%	$38.6217	$38.62	$38.60	$38.60
Purchase #4	$117.77	8.169%	$127.3906	$127.39	$127.40	$127.40
Purchase #5	$202.92	4.830%	$212.721	$212.72	$212.70	$212.70
Purchase #6	$101.41	7.444%	$108.959	$108.96	$108.95	$109.00
Purchase #7	$105.49	12.172%	$118.3302	$118.33	$118.35	$118.30
7 purchase totals =	$848.81		$911.5402	$911.54	$911.55	$911.50