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	$215.36	9.319%	$235.4294	$235.43	$235.45	$235.40
Purchase #2	$201.86	4.828%	$211.6058	$211.61	$211.60	$211.60
Purchase #3	$37.94	12.602%	$42.7212	$42.72	$42.70	$42.70
Purchase #4	$64.45	8.336%	$69.8226	$69.82	$69.80	$69.80
Purchase #5	$169.82	10.415%	$187.5068	$187.51	$187.50	$187.50
Purchase #6	$74.70	4.727%	$78.2311	$78.23	$78.25	$78.20
Purchase #7	$107.72	3.644%	$111.6453	$111.65	$111.65	$111.60
7 purchase totals =	$871.85		$936.9622	$936.97	$936.95	$936.80