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	$147.59	4.649%	$154.4515	$154.45	$154.45	$154.50
Purchase #2	$153.31	8.852%	$166.881	$166.88	$166.90	$166.90
Purchase #3	$176.54	4.651%	$184.7509	$184.75	$184.75	$184.80
Purchase #4	$131.78	4.580%	$137.8155	$137.82	$137.80	$137.80
Purchase #5	$207.35	11.146%	$230.4612	$230.46	$230.45	$230.50
Purchase #6	$140.60	11.134%	$156.2544	$156.25	$156.25	$156.30
Purchase #7	$47.73	7.567%	$51.3417	$51.34	$51.35	$51.30
7 purchase totals =	$1,004.90		$1,081.9562	$1,081.95	$1,081.95	$1,082.10