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	$122.92	7.767%	$132.4672	$132.47	$132.45	$132.50
Purchase #2	$220.40	11.815%	$246.4403	$246.44	$246.45	$246.40
Purchase #3	$162.70	5.253%	$171.2466	$171.25	$171.25	$171.20
Purchase #4	$230.32	3.382%	$238.1094	$238.11	$238.10	$238.10
Purchase #5	$138.92	9.277%	$151.8076	$151.81	$151.80	$151.80
Purchase #6	$111.41	11.587%	$124.3191	$124.32	$124.30	$124.30
Purchase #7	$98.61	6.601%	$105.1192	$105.12	$105.10	$105.10
7 purchase totals =	$1,085.28		$1,169.5094	$1,169.52	$1,169.45	$1,169.40