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	$187.80	10.673%	$207.8439	$207.84	$207.85	$207.80
Purchase #2	$181.93	5.836%	$192.5474	$192.55	$192.55	$192.50
Purchase #3	$155.88	5.603%	$164.614	$164.61	$164.60	$164.60
Purchase #4	$73.68	9.311%	$80.5403	$80.54	$80.55	$80.50
Purchase #5	$64.75	4.799%	$67.8574	$67.86	$67.85	$67.90
Purchase #6	$193.74	7.595%	$208.4546	$208.45	$208.45	$208.50
Purchase #7	$83.70	12.857%	$94.4613	$94.46	$94.45	$94.50
7 purchase totals =	$941.48		$1,016.3189	$1,016.31	$1,016.30	$1,016.30