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	$187.65	13.106%	$212.2434	$212.24	$212.25	$212.20
Purchase #2	$25.51	7.716%	$27.4784	$27.48	$27.50	$27.50
Purchase #3	$173.90	10.189%	$191.6187	$191.62	$191.60	$191.60
Purchase #4	$131.84	12.723%	$148.614	$148.61	$148.60	$148.60
Purchase #5	$118.60	10.154%	$130.6426	$130.64	$130.65	$130.60
Purchase #6	$111.74	7.446%	$120.0602	$120.06	$120.05	$120.10
Purchase #7	$174.85	6.102%	$185.5193	$185.52	$185.50	$185.50
7 purchase totals =	$924.09		$1,016.1766	$1,016.17	$1,016.15	$1,016.10