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	$145.28	13.540%	$164.9509	$164.95	$164.95	$165.00
Purchase #2	$68.91	3.139%	$71.0731	$71.07	$71.05	$71.10
Purchase #3	$20.88	13.556%	$23.7105	$23.71	$23.70	$23.70
Purchase #4	$204.58	10.187%	$225.4206	$225.42	$225.40	$225.40
Purchase #5	$64.76	12.129%	$72.6147	$72.61	$72.60	$72.60
Purchase #6	$106.78	9.516%	$116.9412	$116.94	$116.95	$116.90
Purchase #7	$138.69	10.160%	$152.7809	$152.78	$152.80	$152.80
7 purchase totals =	$749.88		$827.4919	$827.48	$827.45	$827.50