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	$196.42	5.140%	$206.516	$206.52	$206.50	$206.50
Purchase #2	$224.84	11.455%	$250.5954	$250.60	$250.60	$250.60
Purchase #3	$193.29	13.182%	$218.7695	$218.77	$218.75	$218.80
Purchase #4	$113.95	9.437%	$124.7035	$124.70	$124.70	$124.70
Purchase #5	$167.91	10.182%	$185.0066	$185.01	$185.00	$185.00
Purchase #6	$169.72	13.874%	$193.267	$193.27	$193.25	$193.30
Purchase #7	$52.77	12.352%	$59.2882	$59.29	$59.30	$59.30
7 purchase totals =	$1,118.90		$1,238.1462	$1,238.16	$1,238.10	$1,238.20