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	$47.50	3.231%	$49.0347	$49.03	$49.05	$49.00
Purchase #2	$180.77	4.295%	$188.5341	$188.53	$188.55	$188.50
Purchase #3	$141.92	9.798%	$155.8253	$155.83	$155.85	$155.80
Purchase #4	$96.57	8.789%	$105.0575	$105.06	$105.05	$105.10
Purchase #5	$122.45	7.158%	$131.215	$131.22	$131.20	$131.20
Purchase #6	$85.72	12.539%	$96.4684	$96.47	$96.45	$96.50
Purchase #7	$9.66	13.255%	$10.9404	$10.94	$10.95	$10.90
7 purchase totals =	$684.59		$737.0754	$737.08	$737.10	$737.00