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	$227.87	12.393%	$256.1099	$256.11	$256.10	$256.10
Purchase #2	$152.63	9.660%	$167.3741	$167.37	$167.35	$167.40
Purchase #3	$57.55	4.662%	$60.233	$60.23	$60.25	$60.20
Purchase #4	$214.35	6.160%	$227.554	$227.55	$227.55	$227.60
Purchase #5	$87.47	3.706%	$90.7116	$90.71	$90.70	$90.70
Purchase #6	$176.25	10.322%	$194.4425	$194.44	$194.45	$194.40
Purchase #7	$24.59	11.830%	$27.499	$27.50	$27.50	$27.50
7 purchase totals =	$940.71		$1,023.9241	$1,023.91	$1,023.90	$1,023.90