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	$62.34	4.712%	$65.2775	$65.28	$65.30	$65.30
Purchase #2	$129.29	13.251%	$146.4222	$146.42	$146.40	$146.40
Purchase #3	$125.84	5.580%	$132.8619	$132.86	$132.85	$132.90
Purchase #4	$249.94	7.555%	$268.823	$268.82	$268.80	$268.80
Purchase #5	$145.47	3.286%	$150.2501	$150.25	$150.25	$150.30
Purchase #6	$31.85	5.874%	$33.7209	$33.72	$33.70	$33.70
Purchase #7	$162.42	4.710%	$170.07	$170.07	$170.05	$170.10
7 purchase totals =	$907.15		$967.4256	$967.42	$967.35	$967.50