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	$28.71	11.250%	$31.9399	$31.94	$31.95	$31.90
Purchase #2	$97.40	7.376%	$104.5842	$104.58	$104.60	$104.60
Purchase #3	$196.93	6.829%	$210.3783	$210.38	$210.40	$210.40
Purchase #4	$204.58	3.377%	$211.4887	$211.49	$211.50	$211.50
Purchase #5	$241.32	7.447%	$259.2911	$259.29	$259.30	$259.30
Purchase #6	$223.81	5.125%	$235.2803	$235.28	$235.30	$235.30
Purchase #7	$70.41	11.434%	$78.4607	$78.46	$78.45	$78.50
7 purchase totals =	$1,063.16		$1,131.4232	$1,131.42	$1,131.50	$1,131.50