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	$87.60	5.867%	$92.7395	$92.74	$92.75	$92.70
Purchase #2	$18.28	12.419%	$20.5502	$20.55	$20.55	$20.60
Purchase #3	$229.50	12.119%	$257.3131	$257.31	$257.30	$257.30
Purchase #4	$100.68	10.828%	$111.5816	$111.58	$111.60	$111.60
Purchase #5	$131.75	8.642%	$143.1358	$143.14	$143.15	$143.10
Purchase #6	$80.47	3.499%	$83.2856	$83.29	$83.30	$83.30
Purchase #7	$61.25	4.210%	$63.8286	$63.83	$63.85	$63.80
7 purchase totals =	$709.53		$772.4344	$772.44	$772.50	$772.40