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	$140.79	12.232%	$158.0114	$158.01	$158.00	$158.00
Purchase #2	$206.79	3.389%	$213.7981	$213.80	$213.80	$213.80
Purchase #3	$123.42	3.290%	$127.4805	$127.48	$127.50	$127.50
Purchase #4	$127.40	10.369%	$140.6101	$140.61	$140.60	$140.60
Purchase #5	$139.32	11.647%	$155.5466	$155.55	$155.55	$155.50
Purchase #6	$167.43	3.204%	$172.7945	$172.79	$172.80	$172.80
Purchase #7	$47.69	9.536%	$52.2377	$52.24	$52.25	$52.20
7 purchase totals =	$952.84		$1,020.4789	$1,020.48	$1,020.50	$1,020.40