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	$163.56	6.348%	$173.9428	$173.94	$173.95	$173.90
Purchase #2	$9.60	7.197%	$10.2909	$10.29	$10.30	$10.30
Purchase #3	$99.97	8.586%	$108.5534	$108.55	$108.55	$108.60
Purchase #4	$78.57	13.384%	$89.0858	$89.09	$89.10	$89.10
Purchase #5	$95.65	10.296%	$105.4981	$105.50	$105.50	$105.50
Purchase #6	$167.31	7.102%	$179.1924	$179.19	$179.20	$179.20
Purchase #7	$180.95	5.502%	$190.9059	$190.91	$190.90	$190.90
7 purchase totals =	$795.61		$857.4693	$857.47	$857.50	$857.50