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	$103.71	4.394%	$108.267	$108.27	$108.25	$108.30
Purchase #2	$155.31	11.326%	$172.9004	$172.90	$172.90	$172.90
Purchase #3	$172.95	4.620%	$180.9403	$180.94	$180.95	$180.90
Purchase #4	$114.92	5.678%	$121.4452	$121.45	$121.45	$121.40
Purchase #5	$12.30	6.300%	$13.0749	$13.07	$13.05	$13.10
Purchase #6	$222.31	6.773%	$237.3671	$237.37	$237.35	$237.40
Purchase #7	$190.31	12.371%	$213.8533	$213.85	$213.85	$213.90
7 purchase totals =	$971.81		$1,047.8482	$1,047.85	$1,047.80	$1,047.90