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	$151.55	4.656%	$158.6062	$158.61	$158.60	$158.60
Purchase #2	$74.55	3.134%	$76.8864	$76.89	$76.90	$76.90
Purchase #3	$84.26	6.328%	$89.592	$89.59	$89.60	$89.60
Purchase #4	$9.97	6.351%	$10.6032	$10.60	$10.60	$10.60
Purchase #5	$11.30	5.474%	$11.9186	$11.92	$11.90	$11.90
Purchase #6	$105.88	4.402%	$110.5408	$110.54	$110.55	$110.50
Purchase #7	$237.28	10.431%	$262.0307	$262.03	$262.05	$262.00
7 purchase totals =	$674.79		$720.1779	$720.18	$720.20	$720.10