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	$165.32	12.635%	$186.2082	$186.21	$186.20	$186.20
Purchase #2	$220.26	10.796%	$244.0393	$244.04	$244.05	$244.00
Purchase #3	$181.79	5.202%	$191.2467	$191.25	$191.25	$191.20
Purchase #4	$176.99	13.333%	$200.5881	$200.59	$200.60	$200.60
Purchase #5	$73.61	6.810%	$78.6228	$78.62	$78.60	$78.60
Purchase #6	$10.31	12.723%	$11.6217	$11.62	$11.60	$11.60
Purchase #7	$115.65	12.786%	$130.437	$130.44	$130.45	$130.40
7 purchase totals =	$943.93		$1,042.7638	$1,042.77	$1,042.75	$1,042.60