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	$107.75	13.485%	$122.2801	$122.28	$122.30	$122.30
Purchase #2	$91.55	9.550%	$100.293	$100.29	$100.30	$100.30
Purchase #3	$63.81	4.495%	$66.6783	$66.68	$66.70	$66.70
Purchase #4	$126.62	13.500%	$143.7137	$143.71	$143.70	$143.70
Purchase #5	$35.43	6.380%	$37.6904	$37.69	$37.70	$37.70
Purchase #6	$158.48	6.297%	$168.4595	$168.46	$168.45	$168.50
Purchase #7	$75.68	3.450%	$78.291	$78.29	$78.30	$78.30
7 purchase totals =	$659.32		$717.4060	$717.40	$717.45	$717.50