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	$57.88	9.612%	$63.4434	$63.44	$63.45	$63.40
Purchase #2	$85.97	4.220%	$89.5979	$89.60	$89.60	$89.60
Purchase #3	$76.64	7.393%	$82.306	$82.31	$82.30	$82.30
Purchase #4	$104.76	6.449%	$111.516	$111.52	$111.50	$111.50
Purchase #5	$167.82	13.575%	$190.6016	$190.60	$190.60	$190.60
Purchase #6	$20.66	10.148%	$22.7566	$22.76	$22.75	$22.80
Purchase #7	$123.73	5.287%	$130.2716	$130.27	$130.25	$130.30
7 purchase totals =	$637.46		$690.4931	$690.50	$690.45	$690.50