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	$99.72	11.616%	$111.3035	$111.30	$111.30	$111.30
Purchase #2	$11.40	6.497%	$12.1407	$12.14	$12.15	$12.10
Purchase #3	$141.35	13.859%	$160.9397	$160.94	$160.95	$160.90
Purchase #4	$150.78	6.707%	$160.8928	$160.89	$160.90	$160.90
Purchase #5	$242.70	11.523%	$270.6663	$270.67	$270.65	$270.70
Purchase #6	$141.32	9.278%	$154.4317	$154.43	$154.45	$154.40
Purchase #7	$82.41	11.722%	$92.0701	$92.07	$92.05	$92.10
7 purchase totals =	$869.68		$962.4448	$962.44	$962.45	$962.40