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	$168.52	6.105%	$178.8081	$178.81	$178.80	$178.80
Purchase #2	$24.65	3.456%	$25.5019	$25.50	$25.50	$25.50
Purchase #3	$228.89	6.755%	$244.3515	$244.35	$244.35	$244.40
Purchase #4	$11.88	9.726%	$13.0354	$13.04	$13.05	$13.00
Purchase #5	$232.55	13.154%	$263.1396	$263.14	$263.15	$263.10
Purchase #6	$88.44	13.328%	$100.2273	$100.23	$100.25	$100.20
Purchase #7	$160.32	13.402%	$181.8061	$181.81	$181.80	$181.80
7 purchase totals =	$915.25		$1,006.8699	$1,006.88	$1,006.90	$1,006.80