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	$121.75	4.747%	$127.5295	$127.53	$127.55	$127.50
Purchase #2	$146.99	5.745%	$155.4346	$155.43	$155.45	$155.40
Purchase #3	$111.69	12.114%	$125.2201	$125.22	$125.20	$125.20
Purchase #4	$159.41	8.193%	$172.4705	$172.47	$172.45	$172.50
Purchase #5	$82.67	4.631%	$86.4984	$86.50	$86.50	$86.50
Purchase #6	$164.89	11.309%	$183.5374	$183.54	$183.55	$183.50
Purchase #7	$72.73	8.217%	$78.7062	$78.71	$78.70	$78.70
7 purchase totals =	$860.13		$929.3967	$929.40	$929.40	$929.30