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	$224.42	6.416%	$238.8188	$238.82	$238.80	$238.80
Purchase #2	$34.83	12.804%	$39.2896	$39.29	$39.30	$39.30
Purchase #3	$227.31	3.561%	$235.4045	$235.40	$235.40	$235.40
Purchase #4	$159.55	9.179%	$174.1951	$174.20	$174.20	$174.20
Purchase #5	$155.80	10.730%	$172.5173	$172.52	$172.50	$172.50
Purchase #6	$118.33	12.646%	$133.294	$133.29	$133.30	$133.30
Purchase #7	$65.70	10.741%	$72.7568	$72.76	$72.75	$72.80
7 purchase totals =	$985.94		$1,066.2761	$1,066.28	$1,066.25	$1,066.30