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	$215.59	10.283%	$237.7591	$237.76	$237.75	$237.80
Purchase #2	$138.27	4.587%	$144.6124	$144.61	$144.60	$144.60
Purchase #3	$115.63	11.326%	$128.7263	$128.73	$128.75	$128.70
Purchase #4	$102.88	8.285%	$111.4036	$111.40	$111.40	$111.40
Purchase #5	$167.56	3.609%	$173.6072	$173.61	$173.60	$173.60
Purchase #6	$19.35	5.676%	$20.4483	$20.45	$20.45	$20.40
Purchase #7	$101.64	9.122%	$110.9116	$110.91	$110.90	$110.90
7 purchase totals =	$860.92		$927.4685	$927.47	$927.45	$927.40