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	$72.44	8.630%	$78.6916	$78.69	$78.70	$78.70
Purchase #2	$154.83	12.758%	$174.5832	$174.58	$174.60	$174.60
Purchase #3	$94.81	10.459%	$104.7262	$104.73	$104.75	$104.70
Purchase #4	$214.44	9.104%	$233.9626	$233.96	$233.95	$234.00
Purchase #5	$203.50	3.822%	$211.2778	$211.28	$211.30	$211.30
Purchase #6	$241.71	13.401%	$274.1016	$274.10	$274.10	$274.10
Purchase #7	$158.63	10.845%	$175.8334	$175.83	$175.85	$175.80
7 purchase totals =	$1,140.36		$1,253.1764	$1,253.17	$1,253.25	$1,253.20