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	$144.43	10.431%	$159.4955	$159.50	$159.50	$159.50
Purchase #2	$89.70	4.123%	$93.3983	$93.40	$93.40	$93.40
Purchase #3	$162.52	5.717%	$171.8113	$171.81	$171.80	$171.80
Purchase #4	$242.78	11.776%	$271.3698	$271.37	$271.35	$271.40
Purchase #5	$131.57	10.378%	$145.2243	$145.22	$145.20	$145.20
Purchase #6	$50.81	7.871%	$54.8093	$54.81	$54.80	$54.80
Purchase #7	$156.90	13.739%	$178.4565	$178.46	$178.45	$178.50
7 purchase totals =	$978.71		$1,074.5650	$1,074.57	$1,074.50	$1,074.60