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	$200.74	3.808%	$208.3842	$208.38	$208.40	$208.40
Purchase #2	$132.59	3.830%	$137.6682	$137.67	$137.65	$137.70
Purchase #3	$248.42	4.518%	$259.6436	$259.64	$259.65	$259.60
Purchase #4	$150.84	12.602%	$169.8489	$169.85	$169.85	$169.80
Purchase #5	$246.97	11.405%	$275.1369	$275.14	$275.15	$275.10
Purchase #6	$66.63	9.759%	$73.1324	$73.13	$73.15	$73.10
Purchase #7	$59.86	9.571%	$65.5892	$65.59	$65.60	$65.60
7 purchase totals =	$1,106.05		$1,189.4034	$1,189.40	$1,189.45	$1,189.30