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	$165.50	3.623%	$171.4961	$171.50	$171.50	$171.50
Purchase #2	$61.43	5.847%	$65.0218	$65.02	$65.00	$65.00
Purchase #3	$123.64	3.849%	$128.3989	$128.40	$128.40	$128.40
Purchase #4	$85.75	10.376%	$94.6474	$94.65	$94.65	$94.60
Purchase #5	$143.51	7.127%	$153.738	$153.74	$153.75	$153.70
Purchase #6	$231.30	4.561%	$241.8496	$241.85	$241.85	$241.80
Purchase #7	$73.85	6.778%	$78.8556	$78.86	$78.85	$78.90
7 purchase totals =	$884.98		$934.0074	$934.02	$934.00	$933.90