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	$223.29	8.332%	$241.8945	$241.89	$241.90	$241.90
Purchase #2	$185.57	3.521%	$192.1039	$192.10	$192.10	$192.10
Purchase #3	$226.52	5.665%	$239.3524	$239.35	$239.35	$239.40
Purchase #4	$99.91	6.534%	$106.4381	$106.44	$106.45	$106.40
Purchase #5	$49.86	4.572%	$52.1396	$52.14	$52.15	$52.10
Purchase #6	$191.57	4.871%	$200.9014	$200.90	$200.90	$200.90
Purchase #7	$250.43	12.438%	$281.5785	$281.58	$281.60	$281.60
7 purchase totals =	$1,227.15		$1,314.4084	$1,314.40	$1,314.45	$1,314.40