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	$49.68	5.652%	$52.4879	$52.49	$52.50	$52.50
Purchase #2	$47.47	4.691%	$49.6968	$49.70	$49.70	$49.70
Purchase #3	$126.26	4.664%	$132.1488	$132.15	$132.15	$132.10
Purchase #4	$52.95	3.673%	$54.8949	$54.89	$54.90	$54.90
Purchase #5	$185.98	5.393%	$196.0099	$196.01	$196.00	$196.00
Purchase #6	$151.70	7.199%	$162.6209	$162.62	$162.60	$162.60
Purchase #7	$196.96	13.602%	$223.7505	$223.75	$223.75	$223.80
7 purchase totals =	$811.00		$871.6097	$871.61	$871.60	$871.60