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	$44.78	3.219%	$46.2215	$46.22	$46.20	$46.20
Purchase #2	$9.83	8.114%	$10.6276	$10.63	$10.65	$10.60
Purchase #3	$194.50	7.417%	$208.9261	$208.93	$208.95	$208.90
Purchase #4	$200.28	7.509%	$215.319	$215.32	$215.30	$215.30
Purchase #5	$128.88	6.668%	$137.4737	$137.47	$137.45	$137.50
Purchase #6	$126.30	10.485%	$139.5426	$139.54	$139.55	$139.50
Purchase #7	$44.52	13.136%	$50.3681	$50.37	$50.35	$50.40
7 purchase totals =	$749.09		$808.4786	$808.48	$808.45	$808.40