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	$125.64	8.350%	$136.1309	$136.13	$136.15	$136.10
Purchase #2	$66.58	6.856%	$71.1447	$71.14	$71.15	$71.10
Purchase #3	$153.61	4.188%	$160.0432	$160.04	$160.05	$160.00
Purchase #4	$102.41	9.190%	$111.8215	$111.82	$111.80	$111.80
Purchase #5	$250.80	6.328%	$266.6706	$266.67	$266.65	$266.70
Purchase #6	$152.91	5.495%	$161.3124	$161.31	$161.30	$161.30
Purchase #7	$207.94	8.140%	$224.8663	$224.87	$224.85	$224.90
7 purchase totals =	$1,059.89		$1,131.9896	$1,131.98	$1,131.95	$1,131.90