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	$224.30	13.576%	$254.751	$254.75	$254.75	$254.80
Purchase #2	$143.29	10.471%	$158.2939	$158.29	$158.30	$158.30
Purchase #3	$49.96	4.241%	$52.0788	$52.08	$52.10	$52.10
Purchase #4	$199.61	12.377%	$224.3157	$224.32	$224.30	$224.30
Purchase #5	$179.82	8.712%	$195.4859	$195.49	$195.50	$195.50
Purchase #6	$91.46	7.666%	$98.4713	$98.47	$98.45	$98.50
Purchase #7	$27.60	4.488%	$28.8387	$28.84	$28.85	$28.80
7 purchase totals =	$916.04		$1,012.2353	$1,012.24	$1,012.25	$1,012.30