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	$46.36	8.149%	$50.1379	$50.14	$50.15	$50.10
Purchase #2	$184.64	5.135%	$194.1213	$194.12	$194.10	$194.10
Purchase #3	$163.64	4.161%	$170.4491	$170.45	$170.45	$170.40
Purchase #4	$242.69	10.691%	$268.636	$268.64	$268.65	$268.60
Purchase #5	$182.29	3.471%	$188.6173	$188.62	$188.60	$188.60
Purchase #6	$118.41	7.665%	$127.4861	$127.49	$127.50	$127.50
Purchase #7	$139.52	3.841%	$144.879	$144.88	$144.90	$144.90
7 purchase totals =	$1,077.55		$1,144.3267	$1,144.34	$1,144.35	$1,144.20