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	$132.25	5.371%	$139.3531	$139.35	$139.35	$139.40
Purchase #2	$28.29	4.171%	$29.47	$29.47	$29.45	$29.50
Purchase #3	$105.40	12.401%	$118.4707	$118.47	$118.45	$118.50
Purchase #4	$19.33	10.640%	$21.3867	$21.39	$21.40	$21.40
Purchase #5	$172.25	3.294%	$177.9239	$177.92	$177.90	$177.90
Purchase #6	$131.86	11.199%	$146.627	$146.63	$146.65	$146.60
Purchase #7	$161.70	3.646%	$167.5956	$167.60	$167.60	$167.60
7 purchase totals =	$751.08		$800.8270	$800.83	$800.80	$800.90