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	$242.58	9.202%	$264.9022	$264.90	$264.90	$264.90
Purchase #2	$221.57	7.697%	$238.6242	$238.62	$238.60	$238.60
Purchase #3	$19.72	13.758%	$22.4331	$22.43	$22.45	$22.40
Purchase #4	$159.27	9.819%	$174.9087	$174.91	$174.90	$174.90
Purchase #5	$198.44	13.277%	$224.7869	$224.79	$224.80	$224.80
Purchase #6	$230.86	13.832%	$262.7926	$262.79	$262.80	$262.80
Purchase #7	$38.90	5.247%	$40.9411	$40.94	$40.95	$40.90
7 purchase totals =	$1,111.34		$1,229.3888	$1,229.38	$1,229.40	$1,229.30