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	$160.41	9.351%	$175.4099	$175.41	$175.40	$175.40
Purchase #2	$56.71	4.699%	$59.3748	$59.37	$59.35	$59.40
Purchase #3	$158.82	8.174%	$171.8019	$171.80	$171.80	$171.80
Purchase #4	$32.50	6.771%	$34.7006	$34.70	$34.70	$34.70
Purchase #5	$132.89	8.803%	$144.5883	$144.59	$144.60	$144.60
Purchase #6	$66.29	7.256%	$71.1	$71.10	$71.10	$71.10
Purchase #7	$115.39	13.148%	$130.5615	$130.56	$130.55	$130.60
7 purchase totals =	$723.01		$787.5370	$787.53	$787.50	$787.60