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	$171.64	4.685%	$179.6813	$179.68	$179.70	$179.70
Purchase #2	$56.27	10.732%	$62.3089	$62.31	$62.30	$62.30
Purchase #3	$147.92	9.738%	$162.3244	$162.32	$162.30	$162.30
Purchase #4	$56.57	5.217%	$59.5213	$59.52	$59.50	$59.50
Purchase #5	$147.39	4.821%	$154.4957	$154.50	$154.50	$154.50
Purchase #6	$220.57	11.811%	$246.6215	$246.62	$246.60	$246.60
Purchase #7	$156.28	4.619%	$163.4986	$163.50	$163.50	$163.50
7 purchase totals =	$956.64		$1,028.4517	$1,028.45	$1,028.40	$1,028.40