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	$231.58	8.646%	$251.6024	$251.60	$251.60	$251.60
Purchase #2	$24.47	10.437%	$27.0239	$27.02	$27.00	$27.00
Purchase #3	$132.47	9.446%	$144.9831	$144.98	$145.00	$145.00
Purchase #4	$13.57	3.779%	$14.0828	$14.08	$14.10	$14.10
Purchase #5	$107.30	4.300%	$111.9139	$111.91	$111.90	$111.90
Purchase #6	$86.94	5.291%	$91.54	$91.54	$91.55	$91.50
Purchase #7	$52.88	11.702%	$59.068	$59.07	$59.05	$59.10
7 purchase totals =	$649.21		$700.2141	$700.20	$700.20	$700.20