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	$229.46	12.833%	$258.9066	$258.91	$258.90	$258.90
Purchase #2	$226.27	10.462%	$249.9424	$249.94	$249.95	$249.90
Purchase #3	$68.92	5.212%	$72.5121	$72.51	$72.50	$72.50
Purchase #4	$15.93	4.139%	$16.5893	$16.59	$16.60	$16.60
Purchase #5	$101.31	10.623%	$112.0722	$112.07	$112.05	$112.10
Purchase #6	$91.44	10.745%	$101.2652	$101.27	$101.25	$101.30
Purchase #7	$223.67	11.624%	$249.6694	$249.67	$249.65	$249.70
7 purchase totals =	$957.00		$1,060.9572	$1,060.96	$1,060.90	$1,061.00