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	$169.97	12.642%	$191.4576	$191.46	$191.45	$191.50
Purchase #2	$206.25	12.402%	$231.8291	$231.83	$231.85	$231.80
Purchase #3	$207.60	11.320%	$231.1003	$231.10	$231.10	$231.10
Purchase #4	$52.35	10.340%	$57.763	$57.76	$57.75	$57.80
Purchase #5	$163.42	13.571%	$185.5977	$185.60	$185.60	$185.60
Purchase #6	$177.62	12.675%	$200.1333	$200.13	$200.15	$200.10
Purchase #7	$90.93	11.459%	$101.3497	$101.35	$101.35	$101.30
7 purchase totals =	$1,068.14		$1,199.2307	$1,199.23	$1,199.25	$1,199.20