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	$155.27	7.261%	$166.5442	$166.54	$166.55	$166.50
Purchase #2	$77.64	12.462%	$87.3155	$87.32	$87.30	$87.30
Purchase #3	$106.73	7.355%	$114.58	$114.58	$114.60	$114.60
Purchase #4	$245.30	5.846%	$259.6402	$259.64	$259.65	$259.60
Purchase #5	$153.39	5.767%	$162.236	$162.24	$162.25	$162.20
Purchase #6	$183.29	9.201%	$200.1545	$200.15	$200.15	$200.20
Purchase #7	$75.73	3.650%	$78.4941	$78.49	$78.50	$78.50
7 purchase totals =	$997.35		$1,068.9645	$1,068.96	$1,069.00	$1,068.90