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	$36.93	4.743%	$38.6816	$38.68	$38.70	$38.70
Purchase #2	$229.49	12.429%	$258.0133	$258.01	$258.00	$258.00
Purchase #3	$133.36	12.845%	$150.4901	$150.49	$150.50	$150.50
Purchase #4	$172.31	13.785%	$196.0629	$196.06	$196.05	$196.10
Purchase #5	$250.52	4.602%	$262.0489	$262.05	$262.05	$262.00
Purchase #6	$76.93	6.734%	$82.1105	$82.11	$82.10	$82.10
Purchase #7	$234.25	3.493%	$242.4324	$242.43	$242.45	$242.40
7 purchase totals =	$1,133.79		$1,229.8397	$1,229.83	$1,229.85	$1,229.80