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	$240.45	4.830%	$252.0637	$252.06	$252.05	$252.10
Purchase #2	$232.37	13.568%	$263.898	$263.90	$263.90	$263.90
Purchase #3	$104.79	3.574%	$108.5352	$108.54	$108.55	$108.50
Purchase #4	$10.69	11.151%	$11.882	$11.88	$11.90	$11.90
Purchase #5	$56.57	3.172%	$58.3644	$58.36	$58.35	$58.40
Purchase #6	$126.63	3.693%	$131.3064	$131.31	$131.30	$131.30
Purchase #7	$74.45	10.267%	$82.0938	$82.09	$82.10	$82.10
7 purchase totals =	$845.95		$908.1435	$908.14	$908.15	$908.20