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	$179.67	9.155%	$196.1188	$196.12	$196.10	$196.10
Purchase #2	$88.62	4.641%	$92.7329	$92.73	$92.75	$92.70
Purchase #3	$186.43	12.682%	$210.0731	$210.07	$210.05	$210.10
Purchase #4	$153.97	11.845%	$172.2077	$172.21	$172.20	$172.20
Purchase #5	$30.60	9.608%	$33.54	$33.54	$33.55	$33.50
Purchase #6	$238.43	12.286%	$267.7235	$267.72	$267.70	$267.70
Purchase #7	$50.92	10.467%	$56.2498	$56.25	$56.25	$56.20
7 purchase totals =	$928.64		$1,028.6458	$1,028.64	$1,028.60	$1,028.50