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	$224.70	7.674%	$241.9435	$241.94	$241.95	$241.90
Purchase #2	$158.32	5.172%	$166.5083	$166.51	$166.50	$166.50
Purchase #3	$49.70	6.106%	$52.7347	$52.73	$52.75	$52.70
Purchase #4	$229.90	11.134%	$255.4971	$255.50	$255.50	$255.50
Purchase #5	$151.28	5.672%	$159.8606	$159.86	$159.85	$159.90
Purchase #6	$73.43	10.638%	$81.2415	$81.24	$81.25	$81.20
Purchase #7	$126.33	3.871%	$131.2202	$131.22	$131.20	$131.20
7 purchase totals =	$1,013.66		$1,089.0059	$1,089.00	$1,089.00	$1,088.90