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	$140.33	6.729%	$149.7728	$149.77	$149.75	$149.80
Purchase #2	$96.61	7.156%	$103.5234	$103.52	$103.50	$103.50
Purchase #3	$101.51	9.594%	$111.2489	$111.25	$111.25	$111.20
Purchase #4	$36.57	11.337%	$40.7159	$40.72	$40.70	$40.70
Purchase #5	$196.31	13.252%	$222.325	$222.33	$222.35	$222.30
Purchase #6	$244.25	5.870%	$258.5875	$258.59	$258.60	$258.60
Purchase #7	$116.54	9.633%	$127.7663	$127.77	$127.75	$127.80
7 purchase totals =	$932.12		$1,013.9398	$1,013.95	$1,013.90	$1,013.90