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	$129.77	3.269%	$134.0122	$134.01	$134.00	$134.00
Purchase #2	$193.83	11.766%	$216.636	$216.64	$216.65	$216.60
Purchase #3	$206.83	4.683%	$216.5158	$216.52	$216.50	$216.50
Purchase #4	$37.84	12.177%	$42.4478	$42.45	$42.45	$42.40
Purchase #5	$215.25	12.182%	$241.4718	$241.47	$241.45	$241.50
Purchase #6	$57.68	3.545%	$59.7248	$59.72	$59.70	$59.70
Purchase #7	$37.97	3.317%	$39.2295	$39.23	$39.25	$39.20
7 purchase totals =	$879.17		$950.0379	$950.04	$950.00	$949.90