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	$46.45	10.355%	$51.2599	$51.26	$51.25	$51.30
Purchase #2	$228.70	11.704%	$255.467	$255.47	$255.45	$255.50
Purchase #3	$84.89	13.184%	$96.0819	$96.08	$96.10	$96.10
Purchase #4	$158.83	13.520%	$180.3038	$180.30	$180.30	$180.30
Purchase #5	$149.43	6.617%	$159.3178	$159.32	$159.30	$159.30
Purchase #6	$119.51	6.763%	$127.5925	$127.59	$127.60	$127.60
Purchase #7	$137.97	5.365%	$145.3721	$145.37	$145.35	$145.40
7 purchase totals =	$925.78		$1,015.3950	$1,015.39	$1,015.35	$1,015.50