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	$84.82	6.606%	$90.4232	$90.42	$90.40	$90.40
Purchase #2	$179.67	3.178%	$185.3799	$185.38	$185.40	$185.40
Purchase #3	$146.98	10.439%	$162.3232	$162.32	$162.30	$162.30
Purchase #4	$221.47	10.385%	$244.4697	$244.47	$244.45	$244.50
Purchase #5	$52.40	5.548%	$55.3072	$55.31	$55.30	$55.30
Purchase #6	$175.86	9.501%	$192.5685	$192.57	$192.55	$192.60
Purchase #7	$106.57	11.796%	$119.141	$119.14	$119.15	$119.10
7 purchase totals =	$967.77		$1,049.6127	$1,049.61	$1,049.55	$1,049.60