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	$240.63	7.536%	$258.7639	$258.76	$258.75	$258.80
Purchase #2	$154.82	9.146%	$168.9798	$168.98	$169.00	$169.00
Purchase #3	$82.94	8.446%	$89.9451	$89.95	$89.95	$89.90
Purchase #4	$28.51	13.637%	$32.3979	$32.40	$32.40	$32.40
Purchase #5	$232.86	4.197%	$242.6331	$242.63	$242.65	$242.60
Purchase #6	$237.86	9.235%	$259.8264	$259.83	$259.85	$259.80
Purchase #7	$175.87	8.339%	$190.5358	$190.54	$190.55	$190.50
7 purchase totals =	$1,153.49		$1,243.0820	$1,243.09	$1,243.15	$1,243.00