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	$202.30	7.422%	$217.3147	$217.31	$217.30	$217.30
Purchase #2	$109.34	8.380%	$118.5027	$118.50	$118.50	$118.50
Purchase #3	$181.86	6.765%	$194.1628	$194.16	$194.15	$194.20
Purchase #4	$119.92	3.266%	$123.8366	$123.84	$123.85	$123.80
Purchase #5	$197.60	7.476%	$212.3726	$212.37	$212.35	$212.40
Purchase #6	$49.46	7.739%	$53.2877	$53.29	$53.30	$53.30
Purchase #7	$32.84	13.788%	$37.368	$37.37	$37.35	$37.40
7 purchase totals =	$893.32		$956.8451	$956.84	$956.80	$956.90