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	$244.58	9.352%	$267.4531	$267.45	$267.45	$267.50
Purchase #2	$146.85	9.306%	$160.5159	$160.52	$160.50	$160.50
Purchase #3	$35.87	9.421%	$39.2493	$39.25	$39.25	$39.20
Purchase #4	$191.30	10.491%	$211.3693	$211.37	$211.35	$211.40
Purchase #5	$79.95	7.427%	$85.8879	$85.89	$85.90	$85.90
Purchase #6	$24.56	10.338%	$27.099	$27.10	$27.10	$27.10
Purchase #7	$186.35	6.567%	$198.5876	$198.59	$198.60	$198.60
7 purchase totals =	$909.46		$990.1621	$990.17	$990.15	$990.20