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	$235.89	7.866%	$254.4451	$254.45	$254.45	$254.40
Purchase #2	$61.44	8.802%	$66.8479	$66.85	$66.85	$66.80
Purchase #3	$96.75	3.395%	$100.0347	$100.03	$100.05	$100.00
Purchase #4	$45.52	7.675%	$49.0137	$49.01	$49.00	$49.00
Purchase #5	$184.55	8.848%	$200.879	$200.88	$200.90	$200.90
Purchase #6	$49.54	6.574%	$52.7968	$52.80	$52.80	$52.80
Purchase #7	$67.42	8.840%	$73.3799	$73.38	$73.40	$73.40
7 purchase totals =	$741.11		$797.3971	$797.40	$797.45	$797.30