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	$15.62	10.586%	$17.2735	$17.27	$17.25	$17.30
Purchase #2	$40.48	9.565%	$44.3519	$44.35	$44.35	$44.40
Purchase #3	$74.41	5.453%	$78.4676	$78.47	$78.45	$78.50
Purchase #4	$103.76	6.342%	$110.3405	$110.34	$110.35	$110.30
Purchase #5	$105.49	5.403%	$111.1896	$111.19	$111.20	$111.20
Purchase #6	$29.42	13.167%	$33.2937	$33.29	$33.30	$33.30
Purchase #7	$41.84	6.678%	$44.6341	$44.63	$44.65	$44.60
7 purchase totals =	$411.02		$439.5509	$439.54	$439.55	$439.60