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	$80.88	8.666%	$87.8891	$87.89	$87.90	$87.90
Purchase #2	$196.85	11.440%	$219.3696	$219.37	$219.35	$219.40
Purchase #3	$46.49	5.157%	$48.8875	$48.89	$48.90	$48.90
Purchase #4	$77.62	6.513%	$82.6754	$82.68	$82.70	$82.70
Purchase #5	$11.99	5.240%	$12.6183	$12.62	$12.60	$12.60
Purchase #6	$94.35	5.855%	$99.8742	$99.87	$99.85	$99.90
Purchase #7	$184.77	10.345%	$203.8845	$203.88	$203.90	$203.90
7 purchase totals =	$692.95		$755.1986	$755.20	$755.20	$755.30