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	$130.96	3.867%	$136.0242	$136.02	$136.00	$136.00
Purchase #2	$69.55	3.700%	$72.1234	$72.12	$72.10	$72.10
Purchase #3	$176.44	6.272%	$187.5063	$187.51	$187.50	$187.50
Purchase #4	$11.83	8.500%	$12.8356	$12.84	$12.85	$12.80
Purchase #5	$62.30	5.300%	$65.6019	$65.60	$65.60	$65.60
Purchase #6	$247.90	3.241%	$255.9344	$255.93	$255.95	$255.90
Purchase #7	$136.96	4.864%	$143.6217	$143.62	$143.60	$143.60
7 purchase totals =	$835.94		$873.6475	$873.64	$873.60	$873.50