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	$237.29	7.506%	$255.101	$255.10	$255.10	$255.10
Purchase #2	$164.76	7.467%	$177.0626	$177.06	$177.05	$177.10
Purchase #3	$189.59	4.480%	$198.0836	$198.08	$198.10	$198.10
Purchase #4	$92.26	8.264%	$99.8844	$99.88	$99.90	$99.90
Purchase #5	$189.78	13.539%	$215.4743	$215.47	$215.45	$215.50
Purchase #6	$101.84	9.849%	$111.8702	$111.87	$111.85	$111.90
Purchase #7	$102.71	3.655%	$106.4641	$106.46	$106.45	$106.50
7 purchase totals =	$1,078.23		$1,163.9402	$1,163.92	$1,163.90	$1,164.10