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	$199.70	4.169%	$208.0255	$208.03	$208.05	$208.00
Purchase #2	$100.72	4.650%	$105.4035	$105.40	$105.40	$105.40
Purchase #3	$7.92	13.335%	$8.9761	$8.98	$9.00	$9.00
Purchase #4	$89.56	12.212%	$100.4971	$100.50	$100.50	$100.50
Purchase #5	$228.33	4.732%	$239.1346	$239.13	$239.15	$239.10
Purchase #6	$109.73	12.144%	$123.0556	$123.06	$123.05	$123.10
Purchase #7	$101.98	12.412%	$114.6378	$114.64	$114.65	$114.60
7 purchase totals =	$837.94		$899.7302	$899.74	$899.80	$899.70