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	$142.67	11.126%	$158.5435	$158.54	$158.55	$158.50
Purchase #2	$80.90	9.513%	$88.596	$88.60	$88.60	$88.60
Purchase #3	$16.73	4.365%	$17.4603	$17.46	$17.45	$17.50
Purchase #4	$51.39	5.149%	$54.0361	$54.04	$54.05	$54.00
Purchase #5	$93.47	6.862%	$99.8839	$99.88	$99.90	$99.90
Purchase #6	$145.47	3.475%	$150.5251	$150.53	$150.55	$150.50
Purchase #7	$201.26	4.491%	$210.2986	$210.30	$210.30	$210.30
7 purchase totals =	$731.89		$779.3435	$779.35	$779.40	$779.30