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	$158.68	8.748%	$172.5613	$172.56	$172.55	$172.60
Purchase #2	$215.50	13.222%	$243.9934	$243.99	$244.00	$244.00
Purchase #3	$117.50	5.384%	$123.8262	$123.83	$123.85	$123.80
Purchase #4	$187.32	9.872%	$205.8122	$205.81	$205.80	$205.80
Purchase #5	$77.40	7.591%	$83.2754	$83.28	$83.30	$83.30
Purchase #6	$166.30	13.867%	$189.3608	$189.36	$189.35	$189.40
Purchase #7	$234.44	8.591%	$254.5807	$254.58	$254.60	$254.60
7 purchase totals =	$1,157.14		$1,273.4100	$1,273.41	$1,273.45	$1,273.50