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	$32.32	7.167%	$34.6364	$34.64	$34.65	$34.60
Purchase #2	$33.64	6.357%	$35.7785	$35.78	$35.80	$35.80
Purchase #3	$246.78	3.532%	$255.4963	$255.50	$255.50	$255.50
Purchase #4	$80.43	13.345%	$91.1634	$91.16	$91.15	$91.20
Purchase #5	$98.94	8.768%	$107.6151	$107.62	$107.60	$107.60
Purchase #6	$105.72	5.595%	$111.635	$111.64	$111.65	$111.60
Purchase #7	$110.45	13.403%	$125.2536	$125.25	$125.25	$125.30
7 purchase totals =	$708.28		$761.5783	$761.59	$761.60	$761.60