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	$184.49	11.186%	$205.1271	$205.13	$205.15	$205.10
Purchase #2	$94.28	8.664%	$102.4484	$102.45	$102.45	$102.40
Purchase #3	$158.64	3.413%	$164.0544	$164.05	$164.05	$164.10
Purchase #4	$185.89	7.675%	$200.1571	$200.16	$200.15	$200.20
Purchase #5	$122.36	6.346%	$130.125	$130.13	$130.15	$130.10
Purchase #6	$86.93	13.268%	$98.4639	$98.46	$98.45	$98.50
Purchase #7	$153.89	3.132%	$158.7098	$158.71	$158.70	$158.70
7 purchase totals =	$986.48		$1,059.0857	$1,059.09	$1,059.10	$1,059.10