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	$161.90	12.278%	$181.7781	$181.78	$181.80	$181.80
Purchase #2	$52.72	12.212%	$59.1582	$59.16	$59.15	$59.20
Purchase #3	$128.83	11.150%	$143.1945	$143.19	$143.20	$143.20
Purchase #4	$158.50	3.779%	$164.4897	$164.49	$164.50	$164.50
Purchase #5	$205.78	12.325%	$231.1424	$231.14	$231.15	$231.10
Purchase #6	$42.51	10.457%	$46.9553	$46.96	$46.95	$47.00
Purchase #7	$134.65	5.166%	$141.606	$141.61	$141.60	$141.60
7 purchase totals =	$884.89		$968.3242	$968.33	$968.35	$968.40