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	$210.81	3.164%	$217.48	$217.48	$217.50	$217.50
Purchase #2	$160.83	11.261%	$178.9411	$178.94	$178.95	$178.90
Purchase #3	$99.84	5.290%	$105.1215	$105.12	$105.10	$105.10
Purchase #4	$107.25	11.390%	$119.4658	$119.47	$119.45	$119.50
Purchase #5	$196.92	5.184%	$207.1283	$207.13	$207.15	$207.10
Purchase #6	$144.92	6.451%	$154.2688	$154.27	$154.25	$154.30
Purchase #7	$132.61	13.342%	$150.3028	$150.30	$150.30	$150.30
7 purchase totals =	$1,053.18		$1,132.7083	$1,132.71	$1,132.70	$1,132.70