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	$51.56	5.469%	$54.3798	$54.38	$54.40	$54.40
Purchase #2	$186.98	12.239%	$209.8645	$209.86	$209.85	$209.90
Purchase #3	$171.38	6.601%	$182.6928	$182.69	$182.70	$182.70
Purchase #4	$108.69	5.229%	$114.3734	$114.37	$114.35	$114.40
Purchase #5	$217.70	5.325%	$229.2925	$229.29	$229.30	$229.30
Purchase #6	$102.60	4.638%	$107.3586	$107.36	$107.35	$107.40
Purchase #7	$31.52	12.381%	$35.4225	$35.42	$35.40	$35.40
7 purchase totals =	$870.43		$933.3841	$933.37	$933.35	$933.50