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	$72.37	4.259%	$75.4522	$75.45	$75.45	$75.50
Purchase #2	$225.29	10.533%	$249.0198	$249.02	$249.00	$249.00
Purchase #3	$35.63	5.636%	$37.6381	$37.64	$37.65	$37.60
Purchase #4	$119.59	12.652%	$134.7205	$134.72	$134.70	$134.70
Purchase #5	$56.27	5.393%	$59.3046	$59.30	$59.30	$59.30
Purchase #6	$122.59	12.830%	$138.3183	$138.32	$138.30	$138.30
Purchase #7	$97.61	9.191%	$106.5813	$106.58	$106.60	$106.60
7 purchase totals =	$729.35		$801.0348	$801.03	$801.00	$801.00