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	$56.92	13.239%	$64.4556	$64.46	$64.45	$64.50
Purchase #2	$143.41	4.687%	$150.1316	$150.13	$150.15	$150.10
Purchase #3	$201.64	3.608%	$208.9152	$208.92	$208.90	$208.90
Purchase #4	$185.31	7.665%	$199.514	$199.51	$199.50	$199.50
Purchase #5	$148.40	12.176%	$166.4692	$166.47	$166.45	$166.50
Purchase #6	$66.45	10.166%	$73.2053	$73.21	$73.20	$73.20
Purchase #7	$172.30	4.351%	$179.7968	$179.80	$179.80	$179.80
7 purchase totals =	$974.43		$1,042.4877	$1,042.50	$1,042.45	$1,042.50