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	$159.52	4.350%	$166.4591	$166.46	$166.45	$166.50
Purchase #2	$111.99	6.567%	$119.3444	$119.34	$119.35	$119.30
Purchase #3	$105.65	11.145%	$117.4247	$117.42	$117.40	$117.40
Purchase #4	$78.76	4.704%	$82.4649	$82.46	$82.45	$82.50
Purchase #5	$171.32	3.191%	$176.7868	$176.79	$176.80	$176.80
Purchase #6	$187.76	11.588%	$209.5176	$209.52	$209.50	$209.50
Purchase #7	$165.97	10.861%	$183.996	$184.00	$184.00	$184.00
7 purchase totals =	$980.97		$1,055.9935	$1,055.99	$1,055.95	$1,056.00