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	$32.34	7.363%	$34.7212	$34.72	$34.70	$34.70
Purchase #2	$186.69	5.398%	$196.7675	$196.77	$196.75	$196.80
Purchase #3	$27.47	4.241%	$28.635	$28.64	$28.65	$28.60
Purchase #4	$205.37	5.826%	$217.3349	$217.33	$217.35	$217.30
Purchase #5	$16.44	11.684%	$18.3608	$18.36	$18.35	$18.40
Purchase #6	$32.43	5.245%	$34.131	$34.13	$34.15	$34.10
Purchase #7	$59.33	10.553%	$65.5911	$65.59	$65.60	$65.60
7 purchase totals =	$560.07		$595.5415	$595.54	$595.55	$595.50