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	$174.32	7.352%	$187.136	$187.14	$187.15	$187.10
Purchase #2	$190.39	9.522%	$208.5189	$208.52	$208.50	$208.50
Purchase #3	$149.46	11.625%	$166.8347	$166.83	$166.85	$166.80
Purchase #4	$33.86	4.376%	$35.3417	$35.34	$35.35	$35.30
Purchase #5	$220.42	3.217%	$227.5109	$227.51	$227.50	$227.50
Purchase #6	$142.99	11.493%	$159.4238	$159.42	$159.40	$159.40
Purchase #7	$103.57	8.770%	$112.6531	$112.65	$112.65	$112.70
7 purchase totals =	$1,015.01		$1,097.4191	$1,097.41	$1,097.40	$1,097.30