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	$221.92	13.708%	$252.3408	$252.34	$252.35	$252.30
Purchase #2	$204.46	8.358%	$221.5488	$221.55	$221.55	$221.50
Purchase #3	$96.68	11.649%	$107.9423	$107.94	$107.95	$107.90
Purchase #4	$155.56	10.526%	$171.9342	$171.93	$171.95	$171.90
Purchase #5	$99.39	13.184%	$112.4936	$112.49	$112.50	$112.50
Purchase #6	$103.93	5.179%	$109.3125	$109.31	$109.30	$109.30
Purchase #7	$36.94	10.104%	$40.6724	$40.67	$40.65	$40.70
7 purchase totals =	$918.88		$1,016.2446	$1,016.23	$1,016.25	$1,016.10