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	$228.27	6.325%	$242.7081	$242.71	$242.70	$242.70
Purchase #2	$203.57	9.476%	$222.8603	$222.86	$222.85	$222.90
Purchase #3	$34.57	9.647%	$37.905	$37.91	$37.90	$37.90
Purchase #4	$192.31	8.342%	$208.3525	$208.35	$208.35	$208.40
Purchase #5	$97.45	12.124%	$109.2648	$109.26	$109.25	$109.30
Purchase #6	$230.33	13.379%	$261.1459	$261.15	$261.15	$261.10
Purchase #7	$231.52	5.652%	$244.6055	$244.61	$244.60	$244.60
7 purchase totals =	$1,218.02		$1,326.8421	$1,326.85	$1,326.80	$1,326.90