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	$148.60	4.660%	$155.5248	$155.52	$155.50	$155.50
Purchase #2	$172.54	7.761%	$185.9308	$185.93	$185.95	$185.90
Purchase #3	$177.42	7.268%	$190.3149	$190.31	$190.30	$190.30
Purchase #4	$32.81	7.794%	$35.3672	$35.37	$35.35	$35.40
Purchase #5	$93.90	8.664%	$102.0355	$102.04	$102.05	$102.00
Purchase #6	$70.31	8.432%	$76.2385	$76.24	$76.25	$76.20
Purchase #7	$106.88	4.245%	$111.4171	$111.42	$111.40	$111.40
7 purchase totals =	$802.46		$856.8288	$856.83	$856.80	$856.70