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	$156.37	10.245%	$172.3901	$172.39	$172.40	$172.40
Purchase #2	$11.61	6.561%	$12.3717	$12.37	$12.35	$12.40
Purchase #3	$171.95	4.601%	$179.8614	$179.86	$179.85	$179.90
Purchase #4	$154.57	13.224%	$175.0103	$175.01	$175.00	$175.00
Purchase #5	$34.81	9.764%	$38.2088	$38.21	$38.20	$38.20
Purchase #6	$65.45	11.462%	$72.9519	$72.95	$72.95	$73.00
Purchase #7	$131.57	13.865%	$149.8122	$149.81	$149.80	$149.80
7 purchase totals =	$726.33		$800.6064	$800.60	$800.55	$800.70