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	$6.77	8.302%	$7.332	$7.33	$7.35	$7.30
Purchase #2	$50.88	7.706%	$54.8008	$54.80	$54.80	$54.80
Purchase #3	$205.71	6.799%	$219.6962	$219.70	$219.70	$219.70
Purchase #4	$54.44	3.821%	$56.5202	$56.52	$56.50	$56.50
Purchase #5	$116.41	12.538%	$131.0055	$131.01	$131.00	$131.00
Purchase #6	$46.59	3.289%	$48.1223	$48.12	$48.10	$48.10
Purchase #7	$100.70	10.351%	$111.1235	$111.12	$111.10	$111.10
7 purchase totals =	$581.50		$628.6005	$628.60	$628.55	$628.50