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	$216.64	9.591%	$237.4179	$237.42	$237.40	$237.40
Purchase #2	$151.39	4.838%	$158.7142	$158.71	$158.70	$158.70
Purchase #3	$128.28	13.712%	$145.8698	$145.87	$145.85	$145.90
Purchase #4	$184.65	3.426%	$190.9761	$190.98	$191.00	$191.00
Purchase #5	$14.83	5.270%	$15.6115	$15.61	$15.60	$15.60
Purchase #6	$87.39	4.815%	$91.5978	$91.60	$91.60	$91.60
Purchase #7	$165.33	3.491%	$171.1017	$171.10	$171.10	$171.10
7 purchase totals =	$948.51		$1,011.2890	$1,011.29	$1,011.25	$1,011.30