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	$124.34	8.493%	$134.9002	$134.90	$134.90	$134.90
Purchase #2	$200.74	4.512%	$209.7974	$209.80	$209.80	$209.80
Purchase #3	$25.28	10.789%	$28.0075	$28.01	$28.00	$28.00
Purchase #4	$189.92	3.335%	$196.2538	$196.25	$196.25	$196.30
Purchase #5	$54.47	3.760%	$56.5181	$56.52	$56.50	$56.50
Purchase #6	$235.85	3.632%	$244.4161	$244.42	$244.40	$244.40
Purchase #7	$133.63	9.223%	$145.9547	$145.95	$145.95	$146.00
7 purchase totals =	$964.23		$1,015.8478	$1,015.85	$1,015.80	$1,015.90