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	$102.83	8.540%	$111.6117	$111.61	$111.60	$111.60
Purchase #2	$155.90	6.282%	$165.6936	$165.69	$165.70	$165.70
Purchase #3	$29.48	10.741%	$32.6464	$32.65	$32.65	$32.60
Purchase #4	$210.31	11.746%	$235.013	$235.01	$235.00	$235.00
Purchase #5	$215.60	3.567%	$223.2905	$223.29	$223.30	$223.30
Purchase #6	$49.56	4.792%	$51.9349	$51.93	$51.95	$51.90
Purchase #7	$151.54	9.565%	$166.0348	$166.03	$166.05	$166.00
7 purchase totals =	$915.22		$986.2249	$986.21	$986.25	$986.10