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	$102.37	8.661%	$111.2363	$111.24	$111.25	$111.20
Purchase #2	$193.40	7.371%	$207.6555	$207.66	$207.65	$207.70
Purchase #3	$30.64	10.673%	$33.9102	$33.91	$33.90	$33.90
Purchase #4	$148.86	4.665%	$155.8043	$155.80	$155.80	$155.80
Purchase #5	$41.62	9.549%	$45.5943	$45.59	$45.60	$45.60
Purchase #6	$204.41	11.375%	$227.6616	$227.66	$227.65	$227.70
Purchase #7	$246.42	10.788%	$273.0038	$273.00	$273.00	$273.00
7 purchase totals =	$967.72		$1,054.8660	$1,054.86	$1,054.85	$1,054.90