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	$173.35	4.391%	$180.9618	$180.96	$180.95	$181.00
Purchase #2	$72.49	13.750%	$82.4574	$82.46	$82.45	$82.50
Purchase #3	$106.90	9.382%	$116.9294	$116.93	$116.95	$116.90
Purchase #4	$143.91	8.603%	$156.2906	$156.29	$156.30	$156.30
Purchase #5	$167.71	7.632%	$180.5096	$180.51	$180.50	$180.50
Purchase #6	$90.69	8.384%	$98.2934	$98.29	$98.30	$98.30
Purchase #7	$187.60	4.671%	$196.3628	$196.36	$196.35	$196.40
7 purchase totals =	$942.65		$1,011.8050	$1,011.80	$1,011.80	$1,011.90