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	$206.55	12.251%	$231.8544	$231.85	$231.85	$231.90
Purchase #2	$116.60	12.606%	$131.2986	$131.30	$131.30	$131.30
Purchase #3	$100.42	3.265%	$103.6987	$103.70	$103.70	$103.70
Purchase #4	$76.42	3.683%	$79.2345	$79.23	$79.25	$79.20
Purchase #5	$109.52	4.362%	$114.2973	$114.30	$114.30	$114.30
Purchase #6	$151.69	5.516%	$160.0572	$160.06	$160.05	$160.10
Purchase #7	$173.28	10.270%	$191.0759	$191.08	$191.10	$191.10
7 purchase totals =	$934.48		$1,011.5166	$1,011.52	$1,011.55	$1,011.60