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	$76.40	13.388%	$86.6284	$86.63	$86.65	$86.60
Purchase #2	$68.47	4.117%	$71.2889	$71.29	$71.30	$71.30
Purchase #3	$227.56	13.593%	$258.4922	$258.49	$258.50	$258.50
Purchase #4	$102.43	11.523%	$114.233	$114.23	$114.25	$114.20
Purchase #5	$30.41	5.647%	$32.1273	$32.13	$32.15	$32.10
Purchase #6	$181.92	9.363%	$198.9532	$198.95	$198.95	$199.00
Purchase #7	$160.48	4.404%	$167.5475	$167.55	$167.55	$167.50
7 purchase totals =	$847.67		$929.2705	$929.27	$929.35	$929.20