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	$178.40	5.624%	$188.4332	$188.43	$188.45	$188.40
Purchase #2	$99.79	6.724%	$106.4999	$106.50	$106.50	$106.50
Purchase #3	$73.43	12.720%	$82.7703	$82.77	$82.75	$82.80
Purchase #4	$70.82	7.418%	$76.0734	$76.07	$76.05	$76.10
Purchase #5	$176.73	11.665%	$197.3456	$197.35	$197.35	$197.30
Purchase #6	$151.31	10.705%	$167.5077	$167.51	$167.50	$167.50
Purchase #7	$200.65	9.801%	$220.3157	$220.32	$220.30	$220.30
7 purchase totals =	$951.13		$1,038.9458	$1,038.95	$1,038.90	$1,038.90