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	$214.95	6.584%	$229.1023	$229.10	$229.10	$229.10
Purchase #2	$185.32	11.653%	$206.9153	$206.92	$206.90	$206.90
Purchase #3	$173.29	13.586%	$196.8332	$196.83	$196.85	$196.80
Purchase #4	$205.53	7.204%	$220.3364	$220.34	$220.35	$220.30
Purchase #5	$202.53	9.545%	$221.8615	$221.86	$221.85	$221.90
Purchase #6	$172.37	12.762%	$194.3679	$194.37	$194.35	$194.40
Purchase #7	$106.70	4.365%	$111.3575	$111.36	$111.35	$111.40
7 purchase totals =	$1,260.69		$1,380.7741	$1,380.78	$1,380.75	$1,380.80