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	$248.69	13.526%	$282.3278	$282.33	$282.35	$282.30
Purchase #2	$114.32	7.773%	$123.2061	$123.21	$123.20	$123.20
Purchase #3	$52.29	10.659%	$57.8636	$57.86	$57.85	$57.90
Purchase #4	$40.27	4.293%	$41.9988	$42.00	$42.00	$42.00
Purchase #5	$93.54	13.817%	$106.4644	$106.46	$106.45	$106.50
Purchase #6	$161.25	12.624%	$181.6062	$181.61	$181.60	$181.60
Purchase #7	$165.72	3.315%	$171.2136	$171.21	$171.20	$171.20
7 purchase totals =	$876.08		$964.6805	$964.68	$964.65	$964.70