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	$212.58	9.795%	$233.4022	$233.40	$233.40	$233.40
Purchase #2	$97.49	13.864%	$111.006	$111.01	$111.00	$111.00
Purchase #3	$224.70	7.263%	$241.02	$241.02	$241.00	$241.00
Purchase #4	$59.46	8.836%	$64.7139	$64.71	$64.70	$64.70
Purchase #5	$147.86	12.275%	$166.0098	$166.01	$166.00	$166.00
Purchase #6	$248.70	9.473%	$272.2594	$272.26	$272.25	$272.30
Purchase #7	$151.90	10.840%	$168.366	$168.37	$168.35	$168.40
7 purchase totals =	$1,142.69		$1,256.7773	$1,256.78	$1,256.70	$1,256.80