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	$228.97	4.232%	$238.66	$238.66	$238.65	$238.70
Purchase #2	$81.35	7.477%	$87.4325	$87.43	$87.45	$87.40
Purchase #3	$38.25	13.552%	$43.4336	$43.43	$43.45	$43.40
Purchase #4	$192.51	12.867%	$217.2803	$217.28	$217.30	$217.30
Purchase #5	$150.43	11.304%	$167.4346	$167.43	$167.45	$167.40
Purchase #6	$194.63	8.390%	$210.9595	$210.96	$210.95	$211.00
Purchase #7	$142.88	13.404%	$162.0316	$162.03	$162.05	$162.00
7 purchase totals =	$1,029.02		$1,127.2321	$1,127.22	$1,127.30	$1,127.20