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	$196.96	6.557%	$209.8747	$209.87	$209.85	$209.90
Purchase #2	$190.49	12.348%	$214.0117	$214.01	$214.00	$214.00
Purchase #3	$107.82	6.160%	$114.4617	$114.46	$114.45	$114.50
Purchase #4	$166.38	6.133%	$176.5841	$176.58	$176.60	$176.60
Purchase #5	$187.71	8.838%	$204.2998	$204.30	$204.30	$204.30
Purchase #6	$89.82	12.335%	$100.8993	$100.90	$100.90	$100.90
Purchase #7	$113.95	10.824%	$126.2839	$126.28	$126.30	$126.30
7 purchase totals =	$1,053.13		$1,146.4152	$1,146.40	$1,146.40	$1,146.50