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	$211.74	4.843%	$221.9946	$221.99	$222.00	$222.00
Purchase #2	$171.52	10.868%	$190.1608	$190.16	$190.15	$190.20
Purchase #3	$117.44	12.801%	$132.4735	$132.47	$132.45	$132.50
Purchase #4	$127.79	7.142%	$136.9168	$136.92	$136.90	$136.90
Purchase #5	$97.70	6.571%	$104.1199	$104.12	$104.10	$104.10
Purchase #6	$154.47	11.523%	$172.2696	$172.27	$172.25	$172.30
Purchase #7	$210.51	9.648%	$230.82	$230.82	$230.80	$230.80
7 purchase totals =	$1,091.17		$1,188.7552	$1,188.75	$1,188.65	$1,188.80