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	$132.31	12.828%	$149.2827	$149.28	$149.30	$149.30
Purchase #2	$207.64	13.799%	$236.2922	$236.29	$236.30	$236.30
Purchase #3	$127.27	4.676%	$133.2211	$133.22	$133.20	$133.20
Purchase #4	$152.87	5.131%	$160.7138	$160.71	$160.70	$160.70
Purchase #5	$180.55	8.707%	$196.2705	$196.27	$196.25	$196.30
Purchase #6	$237.98	13.160%	$269.2982	$269.30	$269.30	$269.30
Purchase #7	$11.27	5.105%	$11.8453	$11.85	$11.85	$11.80
7 purchase totals =	$1,049.89		$1,156.9238	$1,156.92	$1,156.90	$1,156.90