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	$206.77	4.645%	$216.3745	$216.37	$216.35	$216.40
Purchase #2	$164.61	7.442%	$176.8603	$176.86	$176.85	$176.90
Purchase #3	$149.38	9.285%	$163.2499	$163.25	$163.25	$163.20
Purchase #4	$38.52	4.814%	$40.3744	$40.37	$40.35	$40.40
Purchase #5	$134.90	13.301%	$152.843	$152.84	$152.85	$152.80
Purchase #6	$127.66	7.411%	$137.1209	$137.12	$137.10	$137.10
Purchase #7	$249.39	12.368%	$280.2346	$280.23	$280.25	$280.20
7 purchase totals =	$1,071.23		$1,167.0576	$1,167.04	$1,167.00	$1,167.00