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	$181.75	10.493%	$200.821	$200.82	$200.80	$200.80
Purchase #2	$70.78	7.812%	$76.3093	$76.31	$76.30	$76.30
Purchase #3	$77.61	5.730%	$82.0571	$82.06	$82.05	$82.10
Purchase #4	$94.67	6.277%	$100.6124	$100.61	$100.60	$100.60
Purchase #5	$43.61	5.598%	$46.0513	$46.05	$46.05	$46.10
Purchase #6	$30.97	7.817%	$33.3909	$33.39	$33.40	$33.40
Purchase #7	$116.53	3.183%	$120.2391	$120.24	$120.25	$120.20
7 purchase totals =	$615.92		$659.4811	$659.48	$659.45	$659.50