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	$143.47	5.182%	$150.9046	$150.90	$150.90	$150.90
Purchase #2	$133.66	3.721%	$138.6335	$138.63	$138.65	$138.60
Purchase #3	$174.45	11.379%	$194.3007	$194.30	$194.30	$194.30
Purchase #4	$247.61	4.228%	$258.079	$258.08	$258.10	$258.10
Purchase #5	$62.57	6.128%	$66.4043	$66.40	$66.40	$66.40
Purchase #6	$72.46	5.339%	$76.3286	$76.33	$76.35	$76.30
Purchase #7	$134.31	12.349%	$150.8959	$150.90	$150.90	$150.90
7 purchase totals =	$968.53		$1,035.5466	$1,035.54	$1,035.60	$1,035.50