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	$143.48	11.702%	$160.27	$160.27	$160.25	$160.30
Purchase #2	$237.97	5.253%	$250.4706	$250.47	$250.45	$250.50
Purchase #3	$126.77	11.627%	$141.5095	$141.51	$141.50	$141.50
Purchase #4	$216.72	4.163%	$225.7421	$225.74	$225.75	$225.70
Purchase #5	$54.32	3.397%	$56.1653	$56.17	$56.15	$56.20
Purchase #6	$98.83	3.838%	$102.6231	$102.62	$102.60	$102.60
Purchase #7	$159.84	5.293%	$168.3003	$168.30	$168.30	$168.30
7 purchase totals =	$1,037.93		$1,105.0809	$1,105.08	$1,105.00	$1,105.10