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	$62.55	3.587%	$64.7937	$64.79	$64.80	$64.80
Purchase #2	$143.39	6.799%	$153.1391	$153.14	$153.15	$153.10
Purchase #3	$191.29	7.402%	$205.4493	$205.45	$205.45	$205.40
Purchase #4	$83.48	7.770%	$89.9664	$89.97	$89.95	$90.00
Purchase #5	$52.93	6.685%	$56.4684	$56.47	$56.45	$56.50
Purchase #6	$200.77	5.248%	$211.3064	$211.31	$211.30	$211.30
Purchase #7	$156.94	10.373%	$173.2194	$173.22	$173.20	$173.20
7 purchase totals =	$891.35		$954.3427	$954.35	$954.30	$954.30