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	$48.66	8.529%	$52.8102	$52.81	$52.80	$52.80
Purchase #2	$19.48	10.242%	$21.4751	$21.48	$21.50	$21.50
Purchase #3	$167.43	4.504%	$174.971	$174.97	$174.95	$175.00
Purchase #4	$98.47	13.143%	$111.4119	$111.41	$111.40	$111.40
Purchase #5	$49.88	11.730%	$55.7309	$55.73	$55.75	$55.70
Purchase #6	$144.93	9.589%	$158.8273	$158.83	$158.85	$158.80
Purchase #7	$120.62	9.128%	$131.6302	$131.63	$131.65	$131.60
7 purchase totals =	$649.47		$706.8566	$706.86	$706.90	$706.80