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	$178.45	5.381%	$188.0524	$188.05	$188.05	$188.10
Purchase #2	$86.78	5.469%	$91.526	$91.53	$91.55	$91.50
Purchase #3	$225.46	4.600%	$235.8312	$235.83	$235.85	$235.80
Purchase #4	$135.68	4.332%	$141.5577	$141.56	$141.55	$141.60
Purchase #5	$121.87	13.128%	$137.8691	$137.87	$137.85	$137.90
Purchase #6	$104.72	9.439%	$114.6045	$114.60	$114.60	$114.60
Purchase #7	$95.57	7.207%	$102.4577	$102.46	$102.45	$102.50
7 purchase totals =	$948.53		$1,011.8986	$1,011.90	$1,011.90	$1,012.00