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	$35.34	4.803%	$37.0374	$37.04	$37.05	$37.00
Purchase #2	$209.54	6.491%	$223.1412	$223.14	$223.15	$223.10
Purchase #3	$161.83	6.385%	$172.1628	$172.16	$172.15	$172.20
Purchase #4	$164.93	8.791%	$179.429	$179.43	$179.45	$179.40
Purchase #5	$44.93	12.624%	$50.602	$50.60	$50.60	$50.60
Purchase #6	$90.78	5.453%	$95.7302	$95.73	$95.75	$95.70
Purchase #7	$235.67	11.844%	$263.5828	$263.58	$263.60	$263.60
7 purchase totals =	$943.02		$1,021.6854	$1,021.68	$1,021.75	$1,021.60