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	$59.89	3.131%	$61.7652	$61.77	$61.75	$61.80
Purchase #2	$192.42	8.512%	$208.7988	$208.80	$208.80	$208.80
Purchase #3	$7.72	11.597%	$8.6153	$8.62	$8.60	$8.60
Purchase #4	$170.60	11.168%	$189.6526	$189.65	$189.65	$189.70
Purchase #5	$183.27	7.163%	$196.3976	$196.40	$196.40	$196.40
Purchase #6	$105.83	11.467%	$117.9655	$117.97	$117.95	$118.00
Purchase #7	$125.72	5.711%	$132.8999	$132.90	$132.90	$132.90
7 purchase totals =	$845.45		$916.0949	$916.11	$916.05	$916.20