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	$206.28	13.545%	$234.2206	$234.22	$234.20	$234.20
Purchase #2	$47.44	12.250%	$53.2514	$53.25	$53.25	$53.30
Purchase #3	$165.67	6.388%	$176.253	$176.25	$176.25	$176.30
Purchase #4	$212.72	7.143%	$227.9146	$227.91	$227.90	$227.90
Purchase #5	$90.44	10.726%	$100.1406	$100.14	$100.15	$100.10
Purchase #6	$49.97	3.690%	$51.8139	$51.81	$51.80	$51.80
Purchase #7	$88.80	11.599%	$99.0999	$99.10	$99.10	$99.10
7 purchase totals =	$861.32		$942.6940	$942.68	$942.65	$942.70