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	$105.64	5.127%	$111.0562	$111.06	$111.05	$111.10
Purchase #2	$15.80	4.518%	$16.5138	$16.51	$16.50	$16.50
Purchase #3	$189.61	11.232%	$210.907	$210.91	$210.90	$210.90
Purchase #4	$14.30	3.137%	$14.7486	$14.75	$14.75	$14.70
Purchase #5	$103.65	5.663%	$109.5197	$109.52	$109.50	$109.50
Purchase #6	$24.50	4.211%	$25.5317	$25.53	$25.55	$25.50
Purchase #7	$16.69	6.423%	$17.762	$17.76	$17.75	$17.80
7 purchase totals =	$470.19		$506.0390	$506.04	$506.00	$506.00