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	$137.61	9.711%	$150.9733	$150.97	$150.95	$151.00
Purchase #2	$49.77	7.121%	$53.3141	$53.31	$53.30	$53.30
Purchase #3	$12.31	9.395%	$13.4665	$13.47	$13.45	$13.50
Purchase #4	$169.70	12.135%	$190.2931	$190.29	$190.30	$190.30
Purchase #5	$121.61	8.346%	$131.7596	$131.76	$131.75	$131.80
Purchase #6	$60.53	3.116%	$62.4161	$62.42	$62.40	$62.40
Purchase #7	$139.41	4.278%	$145.374	$145.37	$145.35	$145.40
7 purchase totals =	$690.94		$747.5967	$747.59	$747.50	$747.70