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	$240.62	10.679%	$266.3158	$266.32	$266.30	$266.30
Purchase #2	$31.42	3.799%	$32.6136	$32.61	$32.60	$32.60
Purchase #3	$144.84	11.131%	$160.9621	$160.96	$160.95	$161.00
Purchase #4	$122.65	4.190%	$127.789	$127.79	$127.80	$127.80
Purchase #5	$57.60	12.622%	$64.8703	$64.87	$64.85	$64.90
Purchase #6	$212.98	3.241%	$219.8827	$219.88	$219.90	$219.90
Purchase #7	$134.96	7.438%	$144.9983	$145.00	$145.00	$145.00
7 purchase totals =	$945.07		$1,017.4318	$1,017.43	$1,017.40	$1,017.50