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	$118.56	4.187%	$123.5241	$123.52	$123.50	$123.50
Purchase #2	$211.58	6.797%	$225.9611	$225.96	$225.95	$226.00
Purchase #3	$127.63	5.665%	$134.8602	$134.86	$134.85	$134.90
Purchase #4	$151.46	10.308%	$167.0725	$167.07	$167.05	$167.10
Purchase #5	$213.86	4.825%	$224.1787	$224.18	$224.20	$224.20
Purchase #6	$74.61	7.728%	$80.3759	$80.38	$80.40	$80.40
Purchase #7	$103.58	9.648%	$113.5734	$113.57	$113.55	$113.60
7 purchase totals =	$1,001.28		$1,069.5459	$1,069.54	$1,069.50	$1,069.70