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	$184.43	11.572%	$205.7722	$205.77	$205.75	$205.80
Purchase #2	$241.34	9.476%	$264.2094	$264.21	$264.20	$264.20
Purchase #3	$104.25	13.709%	$118.5416	$118.54	$118.55	$118.50
Purchase #4	$43.92	4.211%	$45.7695	$45.77	$45.75	$45.80
Purchase #5	$166.87	8.821%	$181.5896	$181.59	$181.60	$181.60
Purchase #6	$187.26	11.762%	$209.2855	$209.29	$209.30	$209.30
Purchase #7	$189.49	12.626%	$213.415	$213.42	$213.40	$213.40
7 purchase totals =	$1,117.56		$1,238.5828	$1,238.59	$1,238.55	$1,238.60