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	$99.29	12.624%	$111.8244	$111.82	$111.80	$111.80
Purchase #2	$59.51	5.447%	$62.7515	$62.75	$62.75	$62.80
Purchase #3	$50.60	12.734%	$57.0434	$57.04	$57.05	$57.00
Purchase #4	$72.47	8.589%	$78.6944	$78.69	$78.70	$78.70
Purchase #5	$230.41	10.564%	$254.7505	$254.75	$254.75	$254.80
Purchase #6	$127.37	3.632%	$131.9961	$132.00	$132.00	$132.00
Purchase #7	$144.45	12.805%	$162.9468	$162.95	$162.95	$162.90
7 purchase totals =	$784.10		$860.0071	$860.00	$860.00	$860.00