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	$32.91	8.107%	$35.578	$35.58	$35.60	$35.60
Purchase #2	$116.76	12.470%	$131.32	$131.32	$131.30	$131.30
Purchase #3	$97.34	6.547%	$103.7128	$103.71	$103.70	$103.70
Purchase #4	$7.54	9.848%	$8.2825	$8.28	$8.30	$8.30
Purchase #5	$85.32	11.654%	$95.2632	$95.26	$95.25	$95.30
Purchase #6	$116.46	13.370%	$132.0307	$132.03	$132.05	$132.00
Purchase #7	$199.72	7.778%	$215.2542	$215.25	$215.25	$215.30
7 purchase totals =	$656.05		$721.4414	$721.43	$721.45	$721.50