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	$191.60	12.725%	$215.9811	$215.98	$216.00	$216.00
Purchase #2	$47.77	11.851%	$53.4312	$53.43	$53.45	$53.40
Purchase #3	$241.31	9.212%	$263.5395	$263.54	$263.55	$263.50
Purchase #4	$65.88	7.222%	$70.6379	$70.64	$70.65	$70.60
Purchase #5	$154.92	3.870%	$160.9154	$160.92	$160.90	$160.90
Purchase #6	$19.50	10.857%	$21.6171	$21.62	$21.60	$21.60
Purchase #7	$166.27	3.111%	$171.4427	$171.44	$171.45	$171.40
7 purchase totals =	$887.25		$957.5649	$957.57	$957.60	$957.40