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	$132.96	9.332%	$145.3678	$145.37	$145.35	$145.40
Purchase #2	$167.61	4.152%	$174.5692	$174.57	$174.55	$174.60
Purchase #3	$133.29	6.495%	$141.9472	$141.95	$141.95	$141.90
Purchase #4	$119.94	10.348%	$132.3514	$132.35	$132.35	$132.40
Purchase #5	$178.27	4.110%	$185.5969	$185.60	$185.60	$185.60
Purchase #6	$38.58	11.864%	$43.1571	$43.16	$43.15	$43.20
Purchase #7	$237.47	11.472%	$264.7126	$264.71	$264.70	$264.70
7 purchase totals =	$1,008.12		$1,087.7022	$1,087.71	$1,087.65	$1,087.80