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	$109.64	5.102%	$115.2338	$115.23	$115.25	$115.20
Purchase #2	$155.36	10.125%	$171.0902	$171.09	$171.10	$171.10
Purchase #3	$161.92	13.328%	$183.5007	$183.50	$183.50	$183.50
Purchase #4	$127.28	12.770%	$143.5337	$143.53	$143.55	$143.50
Purchase #5	$114.66	3.298%	$118.4415	$118.44	$118.45	$118.40
Purchase #6	$158.42	8.217%	$171.4374	$171.44	$171.45	$171.40
Purchase #7	$120.88	5.566%	$127.6082	$127.61	$127.60	$127.60
7 purchase totals =	$948.16		$1,030.8455	$1,030.84	$1,030.90	$1,030.70