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	$57.91	9.856%	$63.6176	$63.62	$63.60	$63.60
Purchase #2	$240.59	11.642%	$268.5995	$268.60	$268.60	$268.60
Purchase #3	$93.86	3.116%	$96.7847	$96.78	$96.80	$96.80
Purchase #4	$149.49	10.198%	$164.735	$164.74	$164.75	$164.70
Purchase #5	$104.93	12.704%	$118.2603	$118.26	$118.25	$118.30
Purchase #6	$89.46	11.265%	$99.5377	$99.54	$99.55	$99.50
Purchase #7	$33.45	4.627%	$34.9977	$35.00	$35.00	$35.00
7 purchase totals =	$769.69		$846.5325	$846.54	$846.55	$846.50