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	$246.25	8.560%	$267.329	$267.33	$267.35	$267.30
Purchase #2	$198.29	11.239%	$220.5758	$220.58	$220.60	$220.60
Purchase #3	$66.85	7.589%	$71.9232	$71.92	$71.90	$71.90
Purchase #4	$166.45	11.369%	$185.3737	$185.37	$185.35	$185.40
Purchase #5	$131.68	7.528%	$141.5929	$141.59	$141.60	$141.60
Purchase #6	$239.44	5.863%	$253.4784	$253.48	$253.50	$253.50
Purchase #7	$213.56	7.249%	$229.041	$229.04	$229.05	$229.00
7 purchase totals =	$1,262.52		$1,369.3140	$1,369.31	$1,369.35	$1,369.30