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	$132.48	11.140%	$147.2383	$147.24	$147.25	$147.20
Purchase #2	$166.67	4.261%	$173.7718	$173.77	$173.75	$173.80
Purchase #3	$194.92	5.356%	$205.3599	$205.36	$205.35	$205.40
Purchase #4	$117.61	11.283%	$130.8799	$130.88	$130.90	$130.90
Purchase #5	$166.49	6.572%	$177.4317	$177.43	$177.45	$177.40
Purchase #6	$13.93	12.641%	$15.6909	$15.69	$15.70	$15.70
Purchase #7	$226.71	10.472%	$250.4511	$250.45	$250.45	$250.50
7 purchase totals =	$1,018.81		$1,100.8236	$1,100.82	$1,100.85	$1,100.90