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	$224.41	4.781%	$235.139	$235.14	$235.15	$235.10
Purchase #2	$214.95	5.313%	$226.3703	$226.37	$226.35	$226.40
Purchase #3	$150.46	7.827%	$162.2365	$162.24	$162.25	$162.20
Purchase #4	$113.64	8.584%	$123.3949	$123.39	$123.40	$123.40
Purchase #5	$36.37	3.536%	$37.656	$37.66	$37.65	$37.70
Purchase #6	$89.57	9.688%	$98.2475	$98.25	$98.25	$98.20
Purchase #7	$160.70	4.268%	$167.5587	$167.56	$167.55	$167.60
7 purchase totals =	$990.10		$1,050.6029	$1,050.61	$1,050.60	$1,050.60