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	$176.50	9.285%	$192.888	$192.89	$192.90	$192.90
Purchase #2	$39.52	6.723%	$42.1769	$42.18	$42.20	$42.20
Purchase #3	$231.31	4.563%	$241.8647	$241.86	$241.85	$241.90
Purchase #4	$154.99	4.382%	$161.7817	$161.78	$161.80	$161.80
Purchase #5	$70.47	11.213%	$78.3718	$78.37	$78.35	$78.40
Purchase #6	$230.73	6.118%	$244.8461	$244.85	$244.85	$244.80
Purchase #7	$225.94	10.330%	$249.2796	$249.28	$249.30	$249.30
7 purchase totals =	$1,129.46		$1,211.2088	$1,211.21	$1,211.25	$1,211.30