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	$132.30	13.350%	$149.9621	$149.96	$149.95	$150.00
Purchase #2	$247.79	6.375%	$263.5866	$263.59	$263.60	$263.60
Purchase #3	$161.60	12.868%	$182.3947	$182.39	$182.40	$182.40
Purchase #4	$19.45	10.482%	$21.4887	$21.49	$21.50	$21.50
Purchase #5	$101.69	7.318%	$109.1317	$109.13	$109.15	$109.10
Purchase #6	$154.68	6.339%	$164.4852	$164.49	$164.50	$164.50
Purchase #7	$158.71	3.739%	$164.6442	$164.64	$164.65	$164.60
7 purchase totals =	$976.22		$1,055.6932	$1,055.69	$1,055.75	$1,055.70