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	$181.50	3.366%	$187.6093	$187.61	$187.60	$187.60
Purchase #2	$83.65	3.110%	$86.2515	$86.25	$86.25	$86.30
Purchase #3	$50.32	8.622%	$54.6586	$54.66	$54.65	$54.70
Purchase #4	$159.26	4.467%	$166.3741	$166.37	$166.35	$166.40
Purchase #5	$75.38	7.235%	$80.8337	$80.83	$80.85	$80.80
Purchase #6	$220.71	9.564%	$241.8187	$241.82	$241.80	$241.80
Purchase #7	$171.65	8.553%	$186.3312	$186.33	$186.35	$186.30
7 purchase totals =	$942.47		$1,003.8771	$1,003.87	$1,003.85	$1,003.90