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	$207.64	10.661%	$229.7765	$229.78	$229.80	$229.80
Purchase #2	$122.80	11.525%	$136.9527	$136.95	$136.95	$137.00
Purchase #3	$98.63	13.137%	$111.587	$111.59	$111.60	$111.60
Purchase #4	$93.56	9.167%	$102.1366	$102.14	$102.15	$102.10
Purchase #5	$178.49	7.302%	$191.5233	$191.52	$191.50	$191.50
Purchase #6	$48.59	7.239%	$52.1074	$52.11	$52.10	$52.10
Purchase #7	$9.57	9.264%	$10.4566	$10.46	$10.45	$10.50
7 purchase totals =	$759.28		$834.5401	$834.55	$834.55	$834.60