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	$223.59	6.307%	$237.6918	$237.69	$237.70	$237.70
Purchase #2	$154.72	3.550%	$160.2126	$160.21	$160.20	$160.20
Purchase #3	$40.30	9.122%	$43.9762	$43.98	$44.00	$44.00
Purchase #4	$105.40	5.862%	$111.5785	$111.58	$111.60	$111.60
Purchase #5	$50.65	8.289%	$54.8484	$54.85	$54.85	$54.80
Purchase #6	$80.79	6.277%	$85.8612	$85.86	$85.85	$85.90
Purchase #7	$125.43	10.436%	$138.5199	$138.52	$138.50	$138.50
7 purchase totals =	$780.88		$832.6886	$832.69	$832.70	$832.70