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	$92.64	13.354%	$105.0111	$105.01	$105.00	$105.00
Purchase #2	$191.52	12.287%	$215.0521	$215.05	$215.05	$215.10
Purchase #3	$85.89	7.724%	$92.5241	$92.52	$92.50	$92.50
Purchase #4	$46.31	4.252%	$48.2791	$48.28	$48.30	$48.30
Purchase #5	$20.51	4.215%	$21.3745	$21.37	$21.35	$21.40
Purchase #6	$210.38	7.651%	$226.4762	$226.48	$226.50	$226.50
Purchase #7	$123.54	11.849%	$138.1783	$138.18	$138.20	$138.20
7 purchase totals =	$770.79		$846.8954	$846.89	$846.90	$847.00