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	$135.40	7.539%	$145.6078	$145.61	$145.60	$145.60
Purchase #2	$31.25	13.421%	$35.4441	$35.44	$35.45	$35.40
Purchase #3	$38.27	12.405%	$43.0174	$43.02	$43.00	$43.00
Purchase #4	$139.97	13.181%	$158.4194	$158.42	$158.40	$158.40
Purchase #5	$100.50	8.706%	$109.2495	$109.25	$109.25	$109.20
Purchase #6	$97.61	7.715%	$105.1406	$105.14	$105.15	$105.10
Purchase #7	$184.81	4.827%	$193.7308	$193.73	$193.75	$193.70
7 purchase totals =	$727.81		$790.6096	$790.61	$790.60	$790.40