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	$234.55	9.548%	$256.9448	$256.94	$256.95	$256.90
Purchase #2	$195.33	8.260%	$211.4643	$211.46	$211.45	$211.50
Purchase #3	$230.47	7.365%	$247.4441	$247.44	$247.45	$247.40
Purchase #4	$110.62	3.563%	$114.5614	$114.56	$114.55	$114.60
Purchase #5	$75.81	8.262%	$82.0734	$82.07	$82.05	$82.10
Purchase #6	$242.86	7.710%	$261.5845	$261.58	$261.60	$261.60
Purchase #7	$60.86	11.351%	$67.7682	$67.77	$67.75	$67.80
7 purchase totals =	$1,150.50		$1,241.8407	$1,241.82	$1,241.80	$1,241.90